input: Write a function to calculate the Fibonacci sequence up to the nth term. If the input is less than 0, return "Incorrect input". If the input is 0, return 0. If the input is 1, return 1. Otherwise, return the nth term in the Fibonacci sequence.
  
  def fibonacci(n): 
      a = 0
      b = 1
      if n < 0: 
          return "Incorrect input"
      elif n == 0: 
          return a 
      elif n == 1: 
          return b 
      else: 
          for i in range(2, n+1): 
              c = a + b 
              a = b 
              b = c 
          return b 
  
  # Test cases
  assert fibonacci(-1) == "Incorrect input"
  assert fibonacci(0) == 0
  assert fibonacci(1) == 1
  assert fibonacci(2) == 1
  assert fibonacci(9) == 34
output: def fibonacci(n): 
      a = 0
      b = 1
      if n < 0: 
          return "Incorrect input"
      elif n == 0: 
          return a 
      elif n == 1: 
          return b 
      else: 
          for i in range(2, n+1): 
              c = a + b 
              a = b 
              b = c 
          return b