
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE BangPatterns #-}

module Main where

import Debug.Trace
--import Data.List
--import qualified Data.Set.Strict as Set
--import qualified Data.Map.Strict as Map

main :: IO ()
main = do
  a <- getLine
  b <- getLine
  --a `traceShow`
  print $ solve a b

solve :: String -> String -> Int
solve as bs = foldr (\(a, b) s -> if a == b then s else s + 1) 0 $ zip as bs
