input: Write a function to find the nth Fibonacci number. If the input is less than 0, print "Incorrect input". If the input is 0, return 0. If the input is 1, return 1. Otherwise, return the sum of the previous two Fibonacci numbers.
  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(0) == 0
  assert Fibonacci(1) == 1
  assert Fibonacci(2) == 1
  assert Fibonacci(5) == 5
  assert Fibonacci(10) == 55
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)