#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import array
import statistics


def main():
    num_a_cand = int(input())
    num_boxes = int(input())
    box_candies = array.array("L", (int(input()) for _ in range(num_boxes)))
    sum_of_candies = num_a_cand + sum(box_candies)
    aim = min(statistics.median_low(box_candies), sum_of_candies // num_boxes)
    print(sum(map(lambda c: abs(c - aim), box_candies)))


if __name__ == '__main__':
    main()