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

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