input: from typing import List
  
  def fibonacci(n: int) -> int:
      """ Compute the nth term in the Fibonacci sequence. 
      >>> fibonacci(9)
      21
      >>> fibonacci(1)
      1
      >>> fibonacci(0)
      0
      >>> fibonacci(-1)
      "Incorrect input"
      """
output:     if n < 0:
          return "Incorrect input"
      elif n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          a, b = 0, 1
          for _ in range(2, n + 1):
              a, b = b, a + b
          return b