import Control.Monad (replicateM)
import Data.List (sort)

solve :: Integer -> Int -> [Integer] -> Integer
solve b n cs = sum $ map (abs . (\x -> mi - x)) cs where
    ave = (b + sum cs) `div` n'
    mid = (cs !! ((n - 1) `div` 2) + cs !! (n `div` 2)) `div` 2
    mi = min ave mid
    n' = fromIntegral n :: Integer

main = do
    b <- readLn :: IO Integer
    n <- readLn :: IO Int
    cs <- sort . map read <$> replicateM n getLine :: IO [Integer]
    print $ solve b n cs