input: Write a function to calculate the nth term in the Fibonacci sequence. If n is less than 0, print "Incorrect input". If n is 0, return 0. If n is 1, return 1. Otherwise, calculate and return the nth term using a loop. If the given n is 9 then return the 9th term in the Fibonacci sequence.
  def fibonacci(n): 
      a = 0
      b = 1
      if n < 0: 
          print("Incorrect input") 
      elif n == 0: 
          return a 
      elif n == 1: 
          return b 
      else: 
          for i in range(2,n): 
              c = a + b 
              a = b 
              b = c 
          return b 
  
  assert fibonacci(9) == 34
output: def fibonacci(n): 
      a = 0
      b = 1
      if n < 0: 
          print("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