input: Write a function to find the nth Fibonacci number. The function should return the Fibonacci number if the input is a non-negative integer, and print "Incorrect input" if the input is negative. If the input is 0, it should return 0, and if the input is 1, it should return 1.
  def Fibonacci(n): 
      if n<0: 
          print("Incorrect input") 
      elif n==0: 
          return 0
      elif n==1: 
          return 1
      else: 
          return Fibonacci(n-1)+Fibonacci(n-2)
  assert Fibonacci(5)==5
  assert Fibonacci(10)==55
  assert Fibonacci(15)==610
  assert Fibonacci(0)==0
  assert Fibonacci(1)==1
output: def Fibonacci(n): 
      if n<0: 
          print("Incorrect input") 
      elif n==0: 
          return 0
      elif n==1: 
          return 1
      else: 
          return Fibonacci(n-1)+Fibonacci(n-2)