import Data.List
import Data.List.Split

readlines :: FilePath -> IO [String]
readlines = fmap (splitOn "\n\n" . init) . readFile

solution2 :: [[String]] -> Int
solution2 = sum . (map $ length . foldr1 intersect)

main = do
    input <- readlines "6.txt"
    print (solution2 $ map (splitOn "\n") input)