import Control.Applicative ((<$>))
import Control.Monad (replicateM)
import Data.List (sort, foldl')

main :: IO ()
main = do
  b <- readLn
  n <- readLn
  solve b n <$> replicateM n (read <$> getLine) >>= print

solve :: Int -> Int -> [Int] -> Int
solve b n cs = foldl' (\x y -> x + (abs (y - (if h < 0 then m' else m)))) 0 cs
  where scs = sort cs
        m = scs !! (n `div` 2)
        m' = (b + sum cs) `div` n
        h = b + sum cs - n * m