import Control.Monad import Data.List rInt :: String -> Int rInt = read pwUp (a,b) (x,y) = (a+x, b+y) main = do n <- readLn ps <- foldr pwUp (0,0) . map ((`divMod` 2) . length) . group . sort . foldr (++) [] . map (map rInt . words) <$> replicateM n getLine print $ fst ps + snd ps `div` 4