import           Data.List (sort, transpose)
import           Data.List.Split (splitOn)

solve :: [[Int]] -> Int
solve = sum . map abs . (\[x, xx] -> zipWith (-) x xx) . map sort

main :: IO ()
main =
  print . solve . transpose . map parseLine . lines =<< readFile "data.txt"
  where
    parseLine = map read . filter (not . null) . splitOn " "