solve :: String -> String -> Int -> Int
solve (s:sx) (t:tx) ans
 | sx == []         = newAns
 | otherwise        = solve sx tx newAns
  where newAns = ans + if s == t then 0 else 1

main :: IO ()
main = do 
 s <- getLine :: IO String
 t <- getLine :: IO String
 print $ solve s t 0