import Data.List (foldl')
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B

main :: IO ()
main = do
    B.getLine
    xs <- B.getLine
    ys <- B.getLine
    print $ foldl' (\acc (x, y) -> if x == y then acc else acc + 1) 0 $ B.zip xs ys