Add exercises that were initially left out

thinkcspy/Chapter-16-Exercises/Problem1_factorial.py

@@ -0,0 +1,12 @@
+# Runestone.Academy thinkcspy course
+# Chapter 16
+# Problem 1
+
+def computeFactorial(number):
+    if number < 0:
+        return
+    elif number > 1:
+        number *= computeFactorial(number - 1)
+        return number
+    else:
+        return 1