# -*- coding: utf-8 -*-
"""
No.198 キャンディー・ボックス２
https://yukicoder.me/problems/no/198

"""
import sys
from sys import stdin
from statistics import median
input = stdin.readline


def solve(B, N, candies):
    candies.sort()
    m = int(median(candies))
    max_avg = (sum(candies) + B) // N
    m = min(m, max_avg)

    res = [abs(x - m) for x in candies]
    return sum(res)


def main(args):
    B = int(input())
    N = int(input())
    candies = [int(input()) for _ in range(N)]
    ans = solve(B, N, candies)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])