input: def factorial(n):
      """ Compute the factorial of a given number using recursion.
      >>> factorial(5)
      120
      >>> factorial(1)
      1
      >>> factorial(3)
      6
      """
      if n == 1:
          return 1
      else:
          return n * factorial(n - 1)
output:     if n == 1:
          return 1
      else:
          return n * factorial(n - 1)