input: Write a function to calculate the nth Fibonacci number. If the input is less than 0, print "Incorrect input". If the input is 0 or 1, return the input as the output. For other inputs, recursively calculate 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(3)==2
  assert Fibonacci(4)==3
  assert Fibonacci(5)==5
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)