module Main where

import Control.Monad (replicateM)
import qualified Data.Map as M

solve :: [String] -> Int
solve =
    M.foldr ((+) . abs) 0
        . foldr (M.unionWith (-)) M.empty
        . map (M.fromListWith (+) . (flip zip (repeat 1)))

main :: IO ()
main = replicateM 2 getLine >>= print . solve