input: 
  def Fibonacci(n):
      """
      Calculate the Fibonacci numbers up to a given number.
      
      >>> Fibonacci(0)
      0
      >>> Fibonacci(1)
      1
      >>> Fibonacci(5)
      5
      >>> Fibonacci(10)
      55
      """
      if n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          return Fibonacci(n - 1) + Fibonacci(n - 2)
  
output:     if n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          return Fibonacci(n - 1) + Fibonacci(n - 2)