input: def Fibonacci(n): 
      """Return the nth Fibonacci number.
      The Fibonacci sequence is defined as F(0) = 0, F(1) = 1, and F(n) = F(n-1) + F(n-2) for n > 1.
      If the input is less than 0, print "Incorrect input".
      >>> Fibonacci(0)
      0
      >>> Fibonacci(1)
      1
      >>> Fibonacci(5)
      5
      >>> Fibonacci(-1)
      "Incorrect input"
      """
      if n<0: 
          return "Incorrect input" 
      elif n==0: 
          return 0
      elif n==1: 
          return 1
      else: 
          return Fibonacci(n-1)+Fibonacci(n-2)
output:     if n<0: 
          return "Incorrect input" 
      elif n==0: 
          return 0
      elif n==1: 
          return 1
      else: 
          return Fibonacci(n-1)+Fibonacci(n-2)