input: def understand_recursion(n: int) -> int:
      """ Define a recursive function to calculate the factorial of a number
      >>> understand_recursion(5)
      120
      >>> understand_recursion(3)
      6
      """
      if n == 1:
          return 1
      else:
          return n * understand_recursion(n - 1)
output:     if n == 1:
          return 1
      else:
          return n * understand_recursion(n - 1)