-- https://adventofcode.com/2024/day/1 [mit dank an philip]

import Data.String
import System.File

getLines : List String -> IO (List String)
getLines s = do eof <- fEOF stdin
                if eof then pure s
                  else getLine >>= getLines . (:: s)
                  
parse : IO (List (List Int))
parse = getLines [] >>= pure . map (catMaybes . map parsePositive . words)

main : IO ()
main = do l <- parse
          case (transpose l) of
            [x , y] => printLn $ sum $
                       zipWith (abs .: (-)) (sort x) (sort y)
            _ => pure ()