import Data.List

wordsWhen :: (a -> Bool) -> [a] -> [[a]]
wordsWhen pred s =
  case dropWhile pred s of
    [] -> []
    s' -> w : wordsWhen pred s''
      where (w, s'') = break pred s'

findBestPos :: [Integer] -> Integer
findBestPos = median

median xs
  | len `mod` 2 == 0
  = div (xs !! (mid-1) + xs !! mid) 2
  | otherwise = xs !! mid
  where len = length xs
        mid = div len 2

solution xs = foldr1 (+) $ map (\x -> abs (x - med)) xs
  where med = findBestPos xs

main = interact $ show . solution . map read . wordsWhen (==',')