module Main where

import Data.List (sort)

type Input  = [[String]]
type Output = String

parse :: String -> Input
parse =
    map words
    . tail
    . lines

solve :: Input -> Output
solve input =
    let
        a' =
            sort
            . head
            $ input

        b' =
            (++ ["."])
            . sort
            . (!! 1)
            $ input
    in
        fst
        . head
        . filter (uncurry (/=))
        $ zip a' b'

render :: Output -> String
render =
    id

main :: IO ()
main =
    interact
        ( render
        . solve
        . parse
        )