input: def understand_recursion(number: int) -> int:
      """ Define a recursive function to calculate the factorial of a given number.
      >>> understand_recursion(5)
      120
      >>> understand_recursion(4)
      24
      """
  
      if number == 1:
          return 1
      else:
          return number * understand_recursion(number - 1)
output:     if number == 1:
          return 1
      else:
          return number * understand_recursion(number - 1)