diff --git a/04_iteration/00_content.ipynb b/04_iteration/00_content.ipynb
index 0171c6c..cc17d58 100644
--- a/04_iteration/00_content.ipynb
+++ b/04_iteration/00_content.ipynb
@@ -163,7 +163,7 @@
     }
    },
    "source": [
-    "As trivial as this seems, a lot of complexity is hidden in this implementation. In particular, the order in which objects are created and de-referenced in memory might not be apparent right away as [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20countdown%28n%29%3A%0A%20%20%20%20if%20n%20%3D%3D%200%3A%0A%20%20%20%20%20%20%20%20print%28%22Happy%20new%20Year!%22%29%0A%20%20%20%20else%3A%0A%20%20%20%20%20%20%20%20print%28n%29%0A%20%20%20%20%20%20%20%20countdown%28n%20-%201%29%0A%0Acountdown%283%29&cumulative=false&curInstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false) shows: Each time `countdown()` is called, Python creates a *new* frame in the part of the memory where it manages all the names. This way, Python *isolates* all the different `n` variables from each other. As new frames are created until we reach the base case, after which the frames are destroyed in the *reversed* order, this is called a **[stack <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_wiki.png\">](https://en.wikipedia.org/wiki/Stack_(abstract_data_type))** of frames in computer science terminology. In simple words, a stack is a last-in-first-out (LIFO) task queue. Each frame has a single parent frame, namely the one whose recursive function call created it."
+    "As trivial as this seems, a lot of complexity is hidden in this implementation. In particular, the order in which objects are created and de-referenced in memory might not be apparent right away as [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20countdown%28n%29%3A%0A%20%20%20%20if%20n%20%3D%3D%200%3A%0A%20%20%20%20%20%20%20%20print%28%22Happy%20new%20Year!%22%29%0A%20%20%20%20else%3A%0A%20%20%20%20%20%20%20%20print%28n%29%0A%20%20%20%20%20%20%20%20countdown%28n%20-%201%29%0A%0Acountdown%283%29&cumulative=false&curstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false) shows: Each time `countdown()` is called, Python creates a *new* frame in the part of the memory where it manages all the names. This way, Python *isolates* all the different `n` variables from each other. As new frames are created until we reach the base case, after which the frames are destroyed in the *reversed* order, this is called a **[stack <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_wiki.png\">](https://en.wikipedia.org/wiki/Stack_(abstract_data_type))** of frames in computer science terminology. In simple words, a stack is a last-in-first-out (LIFO) task queue. Each frame has a single parent frame, namely the one whose recursive function call created it."
    ]
   },
   {
@@ -273,7 +273,7 @@
    "source": [
     "When we read such code, it is often easier not to follow every function call (i.e., `factorial(n - 1)` here) in one's mind but assume we receive a return value as specified in the documentation. Some call this approach a **[leap of faith](http://greenteapress.com/thinkpython2/html/thinkpython2007.html#sec75)**. We practice this already whenever we call built-in functions (e.g., [print() <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](https://docs.python.org/3/library/functions.html#print) or [len() <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](https://docs.python.org/3/library/functions.html#len)) where we would have to read C code in many cases.\n",
     "\n",
-    "To visualize *all* the computational steps of the exemplary `factorial(3)`, we use [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20factorial%28n%29%3A%0A%20%20%20%20if%20n%20%3D%3D%200%3A%0A%20%20%20%20%20%20%20%20return%201%0A%20%20%20%20else%3A%0A%20%20%20%20%20%20%20%20recurse%20%3D%20factorial%28n%20-%201%29%0A%20%20%20%20%20%20%20%20result%20%3D%20n%20*%20recurse%0A%20%20%20%20%20%20%20%20return%20result%0A%0Asolution%20%3D%20factorial%283%29&cumulative=false&curInstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false): The recursion again creates a stack of frames in memory. In contrast to the previous trivial example, each frame leaves a return value in memory after it is destroyed. This return value is then assigned to the `recurse` variable within the parent frame and used to compute `result`."
+    "To visualize *all* the computational steps of the exemplary `factorial(3)`, we use [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20factorial%28n%29%3A%0A%20%20%20%20if%20n%20%3D%3D%200%3A%0A%20%20%20%20%20%20%20%20return%201%0A%20%20%20%20else%3A%0A%20%20%20%20%20%20%20%20recurse%20%3D%20factorial%28n%20-%201%29%0A%20%20%20%20%20%20%20%20result%20%3D%20n%20*%20recurse%0A%20%20%20%20%20%20%20%20return%20result%0A%0Asolution%20%3D%20factorial%283%29&cumulative=false&curstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false): The recursion again creates a stack of frames in memory. In contrast to the previous trivial example, each frame leaves a return value in memory after it is destroyed. This return value is then assigned to the `recurse` variable within the parent frame and used to compute `result`."
    ]
   },
   {
@@ -334,7 +334,7 @@
    "source": [
     "A Pythonista would formulate `factorial()` in a more concise way using the so-called **early exit** pattern: No `else`-clause is needed as reaching a `return` statement ends a function call *immediately*. Furthermore, we do not need the temporary variables `recurse` and `result`.\n",
     "\n",
-    "As [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20factorial%28n%29%3A%0A%20%20%20%20if%20n%20%3D%3D%200%3A%0A%20%20%20%20%20%20%20%20return%201%0A%20%20%20%20return%20n%20*%20factorial%28n%20-%201%29%0A%0Asolution%20%3D%20factorial%283%29&cumulative=false&curInstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false) shows, this implementation is more efficient as it only requires 18 computational steps instead of 24 to calculate `factorial(3)`, an improvement of 25 percent! "
+    "As [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20factorial%28n%29%3A%0A%20%20%20%20if%20n%20%3D%3D%200%3A%0A%20%20%20%20%20%20%20%20return%201%0A%20%20%20%20return%20n%20*%20factorial%28n%20-%201%29%0A%0Asolution%20%3D%20factorial%283%29&cumulative=false&curstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false) shows, this implementation is more efficient as it only requires 18 computational steps instead of 24 to calculate `factorial(3)`, an improvement of 25 percent! "
    ]
   },
   {
@@ -448,9 +448,9 @@
      "text": [
       "Help on built-in function factorial in module math:\n",
       "\n",
-      "factorial(x, /)\n",
-      "    Find x!.\n",
-      "    \n",
+      "factorial(n, /)\n",
+      "    Find n!.\n",
+      "\n",
       "    Raise a ValueError if x is negative or non-integral.\n",
       "\n"
      ]
@@ -675,8 +675,8 @@
      "text": [
       "Help on built-in function gcd in module math:\n",
       "\n",
-      "gcd(x, y, /)\n",
-      "    greatest common divisor of x and y\n",
+      "gcd(*integers)\n",
+      "    Greatest Common Divisor.\n",
       "\n"
      ]
     }
@@ -870,7 +870,7 @@
     }
    },
    "source": [
-    "This implementation is *highly* **inefficient** as small Fibonacci numbers already take a very long time to compute. The reason for this is **exponential growth** in the number of function calls. As [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20fibonacci%28i%29%3A%0A%20%20%20%20if%20i%20%3D%3D%200%3A%0A%20%20%20%20%20%20%20%20return%200%0A%20%20%20%20elif%20i%20%3D%3D%201%3A%0A%20%20%20%20%20%20%20%20return%201%0A%20%20%20%20return%20fibonacci%28i%20-%201%29%20%2B%20fibonacci%28i%20-%202%29%0A%0Arv%20%3D%20fibonacci%285%29&cumulative=false&curInstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false) shows, `fibonacci()` is called again and again with the same `i` arguments.\n",
+    "This implementation is *highly* **inefficient** as small Fibonacci numbers already take a very long time to compute. The reason for this is **exponential growth** in the number of function calls. As [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20fibonacci%28i%29%3A%0A%20%20%20%20if%20i%20%3D%3D%200%3A%0A%20%20%20%20%20%20%20%20return%200%0A%20%20%20%20elif%20i%20%3D%3D%201%3A%0A%20%20%20%20%20%20%20%20return%201%0A%20%20%20%20return%20fibonacci%28i%20-%201%29%20%2B%20fibonacci%28i%20-%202%29%0A%0Arv%20%3D%20fibonacci%285%29&cumulative=false&curstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false) shows, `fibonacci()` is called again and again with the same `i` arguments.\n",
     "\n",
     "To understand this in detail, we have to study algorithms and data structures (e.g., with [this book](https://www.amazon.de/Introduction-Algorithms-Press-Thomas-Cormen/dp/0262033844/ref=sr_1_1?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=1JNE8U0VZGU0O&qid=1569837169&s=gateway&sprefix=algorithms+an%2Caps%2C180&sr=8-1)), a discipline within computer science, and dive into the analysis of **[time complexity of algorithms <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_wiki.png\">](https://en.wikipedia.org/wiki/Time_complexity)**.\n",
     "\n",
@@ -1022,10 +1022,11 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mRecursionError\u001b[0m                            Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-28-62f686a9f8a1>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mrun_forever\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-27-80575699c62c>\u001b[0m in \u001b[0;36mrun_forever\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;32mdef\u001b[0m \u001b[0mrun_forever\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m     \u001b[0;34m\"\"\"Also a pointless function should have a docstring.\"\"\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m     \u001b[0mrun_forever\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "... last 1 frames repeated, from the frame below ...\n",
-      "\u001b[0;32m<ipython-input-27-80575699c62c>\u001b[0m in \u001b[0;36mrun_forever\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;32mdef\u001b[0m \u001b[0mrun_forever\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m     \u001b[0;34m\"\"\"Also a pointless function should have a docstring.\"\"\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m     \u001b[0mrun_forever\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "Cell \u001b[0;32mIn[28], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mrun_forever\u001b[49m\u001b[43m(\u001b[49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[27], line 3\u001b[0m, in \u001b[0;36mrun_forever\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mrun_forever\u001b[39m():\n\u001b[1;32m      2\u001b[0m \u001b[38;5;250m    \u001b[39m\u001b[38;5;124;03m\"\"\"Also a pointless function should have a docstring.\"\"\"\u001b[39;00m\n\u001b[0;32m----> 3\u001b[0m     \u001b[43mrun_forever\u001b[49m\u001b[43m(\u001b[49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[27], line 3\u001b[0m, in \u001b[0;36mrun_forever\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mrun_forever\u001b[39m():\n\u001b[1;32m      2\u001b[0m \u001b[38;5;250m    \u001b[39m\u001b[38;5;124;03m\"\"\"Also a pointless function should have a docstring.\"\"\"\u001b[39;00m\n\u001b[0;32m----> 3\u001b[0m     \u001b[43mrun_forever\u001b[49m\u001b[43m(\u001b[49m\u001b[43m)\u001b[49m\n",
+      "    \u001b[0;31m[... skipping similar frames: run_forever at line 3 (2974 times)]\u001b[0m\n",
+      "Cell \u001b[0;32mIn[27], line 3\u001b[0m, in \u001b[0;36mrun_forever\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mrun_forever\u001b[39m():\n\u001b[1;32m      2\u001b[0m \u001b[38;5;250m    \u001b[39m\u001b[38;5;124;03m\"\"\"Also a pointless function should have a docstring.\"\"\"\u001b[39;00m\n\u001b[0;32m----> 3\u001b[0m     \u001b[43mrun_forever\u001b[49m\u001b[43m(\u001b[49m\u001b[43m)\u001b[49m\n",
       "\u001b[0;31mRecursionError\u001b[0m: maximum recursion depth exceeded"
      ]
     }
@@ -4014,21 +4015,42 @@
       "-2949.9\n",
       "-2950.9\n",
       "-2951.9\n",
-      "-2952.9\n"
+      "-2952.9\n",
+      "-2953.9\n",
+      "-2954.9\n",
+      "-2955.9\n",
+      "-2956.9\n",
+      "-2957.9\n",
+      "-2958.9\n",
+      "-2959.9\n",
+      "-2960.9\n",
+      "-2961.9\n",
+      "-2962.9\n",
+      "-2963.9\n",
+      "-2964.9\n",
+      "-2965.9\n",
+      "-2966.9\n",
+      "-2967.9\n",
+      "-2968.9\n",
+      "-2969.9\n",
+      "-2970.9\n"
      ]
     },
     {
      "ename": "RecursionError",
-     "evalue": "maximum recursion depth exceeded while calling a Python object",
+     "evalue": "maximum recursion depth exceeded",
      "output_type": "error",
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mRecursionError\u001b[0m                            Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-29-43e3ad331761>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mcountdown\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m3.1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-1-10499518927d>\u001b[0m in \u001b[0;36mcountdown\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      9\u001b[0m     \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     10\u001b[0m         \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 11\u001b[0;31m         \u001b[0mcountdown\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m \u001b[0;34m-\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "... last 1 frames repeated, from the frame below ...\n",
-      "\u001b[0;32m<ipython-input-1-10499518927d>\u001b[0m in \u001b[0;36mcountdown\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      9\u001b[0m     \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     10\u001b[0m         \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 11\u001b[0;31m         \u001b[0mcountdown\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m \u001b[0;34m-\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;31mRecursionError\u001b[0m: maximum recursion depth exceeded while calling a Python object"
+      "Cell \u001b[0;32mIn[29], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mcountdown\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m3.1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[1], line 11\u001b[0m, in \u001b[0;36mcountdown\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      9\u001b[0m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[1;32m     10\u001b[0m     \u001b[38;5;28mprint\u001b[39m(n)\n\u001b[0;32m---> 11\u001b[0m     \u001b[43mcountdown\u001b[49m\u001b[43m(\u001b[49m\u001b[43mn\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m-\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[1], line 11\u001b[0m, in \u001b[0;36mcountdown\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      9\u001b[0m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[1;32m     10\u001b[0m     \u001b[38;5;28mprint\u001b[39m(n)\n\u001b[0;32m---> 11\u001b[0m     \u001b[43mcountdown\u001b[49m\u001b[43m(\u001b[49m\u001b[43mn\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m-\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "    \u001b[0;31m[... skipping similar frames: countdown at line 11 (2972 times)]\u001b[0m\n",
+      "Cell \u001b[0;32mIn[1], line 11\u001b[0m, in \u001b[0;36mcountdown\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      9\u001b[0m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[1;32m     10\u001b[0m     \u001b[38;5;28mprint\u001b[39m(n)\n\u001b[0;32m---> 11\u001b[0m     \u001b[43mcountdown\u001b[49m\u001b[43m(\u001b[49m\u001b[43mn\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m-\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[1], line 10\u001b[0m, in \u001b[0;36mcountdown\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      8\u001b[0m     \u001b[38;5;28mprint\u001b[39m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mHappy New Year!\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m      9\u001b[0m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[0;32m---> 10\u001b[0m     \u001b[38;5;28;43mprint\u001b[39;49m\u001b[43m(\u001b[49m\u001b[43mn\u001b[49m\u001b[43m)\u001b[49m\n\u001b[1;32m     11\u001b[0m     countdown(n \u001b[38;5;241m-\u001b[39m \u001b[38;5;241m1\u001b[39m)\n",
+      "File \u001b[0;32m~/Repositories/intro-to-python/.venv/lib/python3.12/site-packages/ipykernel/iostream.py:664\u001b[0m, in \u001b[0;36mOutStream.write\u001b[0;34m(self, string)\u001b[0m\n\u001b[1;32m    655\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mwrite\u001b[39m(\u001b[38;5;28mself\u001b[39m, string: \u001b[38;5;28mstr\u001b[39m) \u001b[38;5;241m-\u001b[39m\u001b[38;5;241m>\u001b[39m Optional[\u001b[38;5;28mint\u001b[39m]:  \u001b[38;5;66;03m# type:ignore[override]\u001b[39;00m\n\u001b[1;32m    656\u001b[0m \u001b[38;5;250m    \u001b[39m\u001b[38;5;124;03m\"\"\"Write to current stream after encoding if necessary\u001b[39;00m\n\u001b[1;32m    657\u001b[0m \n\u001b[1;32m    658\u001b[0m \u001b[38;5;124;03m    Returns\u001b[39;00m\n\u001b[0;32m   (...)\u001b[0m\n\u001b[1;32m    662\u001b[0m \n\u001b[1;32m    663\u001b[0m \u001b[38;5;124;03m    \"\"\"\u001b[39;00m\n\u001b[0;32m--> 664\u001b[0m     parent \u001b[38;5;241m=\u001b[39m \u001b[38;5;28;43mself\u001b[39;49m\u001b[38;5;241;43m.\u001b[39;49m\u001b[43mparent_header\u001b[49m\n\u001b[1;32m    666\u001b[0m     \u001b[38;5;28;01mif\u001b[39;00m \u001b[38;5;129;01mnot\u001b[39;00m \u001b[38;5;28misinstance\u001b[39m(string, \u001b[38;5;28mstr\u001b[39m):\n\u001b[1;32m    667\u001b[0m         msg \u001b[38;5;241m=\u001b[39m \u001b[38;5;124mf\u001b[39m\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mwrite() argument must be str, not \u001b[39m\u001b[38;5;132;01m{\u001b[39;00m\u001b[38;5;28mtype\u001b[39m(string)\u001b[38;5;132;01m}\u001b[39;00m\u001b[38;5;124m\"\u001b[39m  \u001b[38;5;66;03m# type:ignore[unreachable]\u001b[39;00m\n",
+      "\u001b[0;31mRecursionError\u001b[0m: maximum recursion depth exceeded"
      ]
     }
    ],
@@ -4058,16 +4080,17 @@
    "outputs": [
     {
      "ename": "RecursionError",
-     "evalue": "maximum recursion depth exceeded in comparison",
+     "evalue": "maximum recursion depth exceeded",
      "output_type": "error",
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mRecursionError\u001b[0m                            Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-30-188b816be8b6>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m3.1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-6-88d8d933f651>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     10\u001b[0m     \u001b[0;32mif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0;36m0\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     11\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 12\u001b[0;31m     \u001b[0;32mreturn\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m*\u001b[0m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m \u001b[0;34m-\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "... last 1 frames repeated, from the frame below ...\n",
-      "\u001b[0;32m<ipython-input-6-88d8d933f651>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     10\u001b[0m     \u001b[0;32mif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0;36m0\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     11\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 12\u001b[0;31m     \u001b[0;32mreturn\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m*\u001b[0m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m \u001b[0;34m-\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;31mRecursionError\u001b[0m: maximum recursion depth exceeded in comparison"
+      "Cell \u001b[0;32mIn[30], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m3.1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[6], line 12\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     10\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m==\u001b[39m \u001b[38;5;241m0\u001b[39m:\n\u001b[1;32m     11\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m \u001b[38;5;241m1\u001b[39m\n\u001b[0;32m---> 12\u001b[0m \u001b[38;5;28;01mreturn\u001b[39;00m n \u001b[38;5;241m*\u001b[39m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[43mn\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m-\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[6], line 12\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     10\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m==\u001b[39m \u001b[38;5;241m0\u001b[39m:\n\u001b[1;32m     11\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m \u001b[38;5;241m1\u001b[39m\n\u001b[0;32m---> 12\u001b[0m \u001b[38;5;28;01mreturn\u001b[39;00m n \u001b[38;5;241m*\u001b[39m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[43mn\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m-\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "    \u001b[0;31m[... skipping similar frames: factorial at line 12 (2974 times)]\u001b[0m\n",
+      "Cell \u001b[0;32mIn[6], line 12\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     10\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m==\u001b[39m \u001b[38;5;241m0\u001b[39m:\n\u001b[1;32m     11\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m \u001b[38;5;241m1\u001b[39m\n\u001b[0;32m---> 12\u001b[0m \u001b[38;5;28;01mreturn\u001b[39;00m n \u001b[38;5;241m*\u001b[39m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[43mn\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m-\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "\u001b[0;31mRecursionError\u001b[0m: maximum recursion depth exceeded"
      ]
     }
    ],
@@ -4382,8 +4405,8 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-38-188b816be8b6>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m3.1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-35-54b57bc2107d>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     13\u001b[0m     \"\"\"\n\u001b[1;32m     14\u001b[0m     \u001b[0;32mif\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0misinstance\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mint\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 15\u001b[0;31m         \u001b[0;32mraise\u001b[0m \u001b[0mTypeError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Factorial is only defined for integers\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     16\u001b[0m     \u001b[0;32melif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m<\u001b[0m \u001b[0;36m0\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     17\u001b[0m         \u001b[0;32mraise\u001b[0m \u001b[0mValueError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Factorial is not defined for negative integers\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "Cell \u001b[0;32mIn[38], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m3.1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[35], line 15\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[38;5;250m\u001b[39m\u001b[38;5;124;03m\"\"\"Calculate the factorial of a number.\u001b[39;00m\n\u001b[1;32m      3\u001b[0m \n\u001b[1;32m      4\u001b[0m \u001b[38;5;124;03mArgs:\u001b[39;00m\n\u001b[0;32m   (...)\u001b[0m\n\u001b[1;32m     12\u001b[0m \u001b[38;5;124;03m    ValueError: if n is negative\u001b[39;00m\n\u001b[1;32m     13\u001b[0m \u001b[38;5;124;03m\"\"\"\u001b[39;00m\n\u001b[1;32m     14\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m \u001b[38;5;129;01mnot\u001b[39;00m \u001b[38;5;28misinstance\u001b[39m(n, \u001b[38;5;28mint\u001b[39m):\n\u001b[0;32m---> 15\u001b[0m     \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mTypeError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mFactorial is only defined for integers\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     16\u001b[0m \u001b[38;5;28;01melif\u001b[39;00m n \u001b[38;5;241m<\u001b[39m \u001b[38;5;241m0\u001b[39m:\n\u001b[1;32m     17\u001b[0m     \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mValueError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mFactorial is not defined for negative integers\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n",
       "\u001b[0;31mTypeError\u001b[0m: Factorial is only defined for integers"
      ]
     }
@@ -4408,8 +4431,8 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mValueError\u001b[0m                                Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-39-b06b2cada645>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m-\u001b[0m\u001b[0;36m42\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-35-54b57bc2107d>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     15\u001b[0m         \u001b[0;32mraise\u001b[0m \u001b[0mTypeError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Factorial is only defined for integers\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     16\u001b[0m     \u001b[0;32melif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m<\u001b[0m \u001b[0;36m0\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 17\u001b[0;31m         \u001b[0;32mraise\u001b[0m \u001b[0mValueError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Factorial is not defined for negative integers\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     18\u001b[0m     \u001b[0;32melif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0;36m0\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     19\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "Cell \u001b[0;32mIn[39], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m-\u001b[39;49m\u001b[38;5;241;43m42\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[35], line 17\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     15\u001b[0m     \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mTypeError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mFactorial is only defined for integers\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     16\u001b[0m \u001b[38;5;28;01melif\u001b[39;00m n \u001b[38;5;241m<\u001b[39m \u001b[38;5;241m0\u001b[39m:\n\u001b[0;32m---> 17\u001b[0m     \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mValueError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mFactorial is not defined for negative integers\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     18\u001b[0m \u001b[38;5;28;01melif\u001b[39;00m n \u001b[38;5;241m==\u001b[39m \u001b[38;5;241m0\u001b[39m:\n\u001b[1;32m     19\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m \u001b[38;5;241m1\u001b[39m\n",
       "\u001b[0;31mValueError\u001b[0m: Factorial is not defined for negative integers"
      ]
     }
@@ -4445,8 +4468,8 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-40-32f1a9e8cf49>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m3.0\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-35-54b57bc2107d>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     13\u001b[0m     \"\"\"\n\u001b[1;32m     14\u001b[0m     \u001b[0;32mif\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0misinstance\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mint\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 15\u001b[0;31m         \u001b[0;32mraise\u001b[0m \u001b[0mTypeError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Factorial is only defined for integers\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     16\u001b[0m     \u001b[0;32melif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m<\u001b[0m \u001b[0;36m0\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     17\u001b[0m         \u001b[0;32mraise\u001b[0m \u001b[0mValueError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"Factorial is not defined for negative integers\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "Cell \u001b[0;32mIn[40], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m3.0\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[35], line 15\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[38;5;250m\u001b[39m\u001b[38;5;124;03m\"\"\"Calculate the factorial of a number.\u001b[39;00m\n\u001b[1;32m      3\u001b[0m \n\u001b[1;32m      4\u001b[0m \u001b[38;5;124;03mArgs:\u001b[39;00m\n\u001b[0;32m   (...)\u001b[0m\n\u001b[1;32m     12\u001b[0m \u001b[38;5;124;03m    ValueError: if n is negative\u001b[39;00m\n\u001b[1;32m     13\u001b[0m \u001b[38;5;124;03m\"\"\"\u001b[39;00m\n\u001b[1;32m     14\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m \u001b[38;5;129;01mnot\u001b[39;00m \u001b[38;5;28misinstance\u001b[39m(n, \u001b[38;5;28mint\u001b[39m):\n\u001b[0;32m---> 15\u001b[0m     \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mTypeError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mFactorial is only defined for integers\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     16\u001b[0m \u001b[38;5;28;01melif\u001b[39;00m n \u001b[38;5;241m<\u001b[39m \u001b[38;5;241m0\u001b[39m:\n\u001b[1;32m     17\u001b[0m     \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mValueError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mFactorial is not defined for negative integers\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n",
       "\u001b[0;31mTypeError\u001b[0m: Factorial is only defined for integers"
      ]
     }
@@ -4688,8 +4711,8 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-47-188b816be8b6>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m3.1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-45-07dc981a3422>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     13\u001b[0m     \"\"\"\n\u001b[1;32m     14\u001b[0m     \u001b[0;32mif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m!=\u001b[0m \u001b[0mint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 15\u001b[0;31m         \u001b[0;32mraise\u001b[0m \u001b[0mTypeError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"n is not integer-like; it has non-zero decimals\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     16\u001b[0m     \u001b[0mn\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     17\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "Cell \u001b[0;32mIn[47], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m3.1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[45], line 15\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[38;5;250m\u001b[39m\u001b[38;5;124;03m\"\"\"Calculate the factorial of a number.\u001b[39;00m\n\u001b[1;32m      3\u001b[0m \n\u001b[1;32m      4\u001b[0m \u001b[38;5;124;03mArgs:\u001b[39;00m\n\u001b[0;32m   (...)\u001b[0m\n\u001b[1;32m     12\u001b[0m \u001b[38;5;124;03m    ValueError: if n is negative\u001b[39;00m\n\u001b[1;32m     13\u001b[0m \u001b[38;5;124;03m\"\"\"\u001b[39;00m\n\u001b[1;32m     14\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m!=\u001b[39m \u001b[38;5;28mint\u001b[39m(n):\n\u001b[0;32m---> 15\u001b[0m     \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mTypeError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mn is not integer-like; it has non-zero decimals\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     16\u001b[0m n \u001b[38;5;241m=\u001b[39m \u001b[38;5;28mint\u001b[39m(n)\n\u001b[1;32m     18\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m<\u001b[39m \u001b[38;5;241m0\u001b[39m:\n",
       "\u001b[0;31mTypeError\u001b[0m: n is not integer-like; it has non-zero decimals"
      ]
     }
@@ -4725,8 +4748,8 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mValueError\u001b[0m                                Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-48-9a12eb120fc3>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"text\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-45-07dc981a3422>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     12\u001b[0m         \u001b[0mValueError\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0;32mif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;32mis\u001b[0m \u001b[0mnegative\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     13\u001b[0m     \"\"\"\n\u001b[0;32m---> 14\u001b[0;31m     \u001b[0;32mif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m!=\u001b[0m \u001b[0mint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     15\u001b[0m         \u001b[0;32mraise\u001b[0m \u001b[0mTypeError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"n is not integer-like; it has non-zero decimals\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     16\u001b[0m     \u001b[0mn\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "Cell \u001b[0;32mIn[48], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;124;43m\"\u001b[39;49m\u001b[38;5;124;43mtext\u001b[39;49m\u001b[38;5;124;43m\"\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[45], line 14\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mfactorial\u001b[39m(n):\n\u001b[1;32m      2\u001b[0m \u001b[38;5;250m    \u001b[39m\u001b[38;5;124;03m\"\"\"Calculate the factorial of a number.\u001b[39;00m\n\u001b[1;32m      3\u001b[0m \n\u001b[1;32m      4\u001b[0m \u001b[38;5;124;03m    Args:\u001b[39;00m\n\u001b[0;32m   (...)\u001b[0m\n\u001b[1;32m     12\u001b[0m \u001b[38;5;124;03m        ValueError: if n is negative\u001b[39;00m\n\u001b[1;32m     13\u001b[0m \u001b[38;5;124;03m    \"\"\"\u001b[39;00m\n\u001b[0;32m---> 14\u001b[0m     \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m!=\u001b[39m \u001b[38;5;28;43mint\u001b[39;49m\u001b[43m(\u001b[49m\u001b[43mn\u001b[49m\u001b[43m)\u001b[49m:\n\u001b[1;32m     15\u001b[0m         \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mTypeError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mn is not integer-like; it has non-zero decimals\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     16\u001b[0m     n \u001b[38;5;241m=\u001b[39m \u001b[38;5;28mint\u001b[39m(n)\n",
       "\u001b[0;31mValueError\u001b[0m: invalid literal for int() with base 10: 'text'"
      ]
     }
@@ -4801,8 +4824,8 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-50-9a12eb120fc3>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"text\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-49-9ed22b5a2981>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     15\u001b[0m         \u001b[0mcasted_n\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mn\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     16\u001b[0m     \u001b[0;32mexcept\u001b[0m \u001b[0mValueError\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 17\u001b[0;31m         \u001b[0;32mraise\u001b[0m \u001b[0mTypeError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"n cannot be casted as an integer\"\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;32mNone\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     18\u001b[0m     \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     19\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m!=\u001b[0m \u001b[0mcasted_n\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "Cell \u001b[0;32mIn[50], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;124;43m\"\u001b[39;49m\u001b[38;5;124;43mtext\u001b[39;49m\u001b[38;5;124;43m\"\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[49], line 17\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     15\u001b[0m     casted_n \u001b[38;5;241m=\u001b[39m \u001b[38;5;28mint\u001b[39m(n)\n\u001b[1;32m     16\u001b[0m \u001b[38;5;28;01mexcept\u001b[39;00m \u001b[38;5;167;01mValueError\u001b[39;00m:\n\u001b[0;32m---> 17\u001b[0m     \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mTypeError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mn cannot be casted as an integer\u001b[39m\u001b[38;5;124m\"\u001b[39m) \u001b[38;5;28;01mfrom\u001b[39;00m \u001b[38;5;28;01mNone\u001b[39;00m\n\u001b[1;32m     18\u001b[0m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[1;32m     19\u001b[0m     \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m!=\u001b[39m casted_n:\n",
       "\u001b[0;31mTypeError\u001b[0m: n cannot be casted as an integer"
      ]
     }
@@ -4827,8 +4850,8 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-51-188b816be8b6>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mfactorial\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m3.1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-      "\u001b[0;32m<ipython-input-49-9ed22b5a2981>\u001b[0m in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     18\u001b[0m     \u001b[0;32melse\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     19\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mn\u001b[0m \u001b[0;34m!=\u001b[0m \u001b[0mcasted_n\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 20\u001b[0;31m             \u001b[0;32mraise\u001b[0m \u001b[0mTypeError\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"n is not integer-like; it has non-zero decimals\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     21\u001b[0m         \u001b[0mn\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mcasted_n\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     22\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "Cell \u001b[0;32mIn[51], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mfactorial\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m3.1\u001b[39;49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[49], line 20\u001b[0m, in \u001b[0;36mfactorial\u001b[0;34m(n)\u001b[0m\n\u001b[1;32m     18\u001b[0m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[1;32m     19\u001b[0m     \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m!=\u001b[39m casted_n:\n\u001b[0;32m---> 20\u001b[0m         \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mTypeError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mn is not integer-like; it has non-zero decimals\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     21\u001b[0m     n \u001b[38;5;241m=\u001b[39m casted_n\n\u001b[1;32m     23\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m n \u001b[38;5;241m<\u001b[39m \u001b[38;5;241m0\u001b[39m:\n",
       "\u001b[0;31mTypeError\u001b[0m: n is not integer-like; it has non-zero decimals"
      ]
     }
@@ -4887,7 +4910,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.6"
+   "version": "3.12.2"
   },
   "livereveal": {
    "auto_select": "code",
diff --git a/04_iteration/01_exercises.ipynb b/04_iteration/01_exercises.ipynb
index cf4b0ce..28304a9 100644
--- a/04_iteration/01_exercises.ipynb
+++ b/04_iteration/01_exercises.ipynb
@@ -589,7 +589,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.6"
+   "version": "3.12.2"
   },
   "toc": {
    "base_numbering": 1,
diff --git a/04_iteration/02_content.ipynb b/04_iteration/02_content.ipynb
index 7fb3eb3..35ac2cb 100644
--- a/04_iteration/02_content.ipynb
+++ b/04_iteration/02_content.ipynb
@@ -137,7 +137,7 @@
     }
    },
    "source": [
-    "As [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20countdown%28n%29%3A%0A%20%20%20%20while%20n%20!%3D%200%3A%0A%20%20%20%20%20%20%20%20print%28n%29%0A%20%20%20%20%20%20%20%20n%20-%3D%201%0A%0A%20%20%20%20print%28%22Happy%20new%20Year!%22%29%0A%0Acountdown%283%29&cumulative=false&curInstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false) shows, there is a subtle but essential difference in the way a `while` statement is treated in memory: In short, `while` statements can *not* run into a `RecursionError` as only *one* frame is needed to manage the names. After all, there is only *one* function call to be made. For typical day-to-day applications, this difference is, however, not so important *unless* a problem instance becomes so big that a large (i.e., $> 3.000$) number of recursive calls must be made."
+    "As [PythonTutor <img height=\"12\" style=\"display: inline-block\" src=\"../static/link/to_py.png\">](http://pythontutor.com/visualize.html#code=def%20countdown%28n%29%3A%0A%20%20%20%20while%20n%20!%3D%200%3A%0A%20%20%20%20%20%20%20%20print%28n%29%0A%20%20%20%20%20%20%20%20n%20-%3D%201%0A%0A%20%20%20%20print%28%22Happy%20new%20Year!%22%29%0A%0Acountdown%283%29&cumulative=false&curstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false) shows, there is a subtle but essential difference in the way a `while` statement is treated in memory: In short, `while` statements can *not* run into a `RecursionError` as only *one* frame is needed to manage the names. After all, there is only *one* function call to be made. For typical day-to-day applications, this difference is, however, not so important *unless* a problem instance becomes so big that a large (i.e., $> 3.000$) number of recursive calls must be made."
    ]
   },
   {
@@ -1268,7 +1268,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.6"
+   "version": "3.12.2"
   },
   "livereveal": {
    "auto_select": "code",
diff --git a/04_iteration/03_content.ipynb b/04_iteration/03_content.ipynb
index dafbe08..d9bb92f 100644
--- a/04_iteration/03_content.ipynb
+++ b/04_iteration/03_content.ipynb
@@ -959,7 +959,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.6"
+   "version": "3.12.2"
   },
   "livereveal": {
    "auto_select": "code",
diff --git a/04_iteration/04_exercises.ipynb b/04_iteration/04_exercises.ipynb
index 04654bc..8bd97ff 100644
--- a/04_iteration/04_exercises.ipynb
+++ b/04_iteration/04_exercises.ipynb
@@ -382,7 +382,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.6"
+   "version": "3.12.2"
   },
   "toc": {
    "base_numbering": 1,
diff --git a/04_iteration/05_summary.ipynb b/04_iteration/05_summary.ipynb
index 981bfec..18d287d 100644
--- a/04_iteration/05_summary.ipynb
+++ b/04_iteration/05_summary.ipynb
@@ -47,7 +47,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.6"
+   "version": "3.12.2"
   },
   "livereveal": {
    "auto_select": "code",
diff --git a/04_iteration/06_review.ipynb b/04_iteration/06_review.ipynb
index b40647b..2043dcc 100644
--- a/04_iteration/06_review.ipynb
+++ b/04_iteration/06_review.ipynb
@@ -247,7 +247,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.6"
+   "version": "3.12.2"
   },
   "toc": {
    "base_numbering": 1,