comp :: Eq a => (a,a) -> Bool
comp (a,b) = a == b

compList :: Eq a => [a] -> [a] -> [Bool]
compList [] _ = []
compList _ [] = []
compList ss ts = map comp $ zip ss ts

main :: IO ()
main = do
    s <- getLine
    t <- getLine

    let ans = length $ filter (==False) $ compList s t
    print ans