import numpy as np


def main():
    b = int(input())
    n = int(input())
    c = np.array([int(input()) for _ in range(n)], dtype='int64')

    # bが小さいと中央値np.median(c)を実現できない。
    # n * x = sum(c) + bをみたすxと中央値の小さい方を作る
    x = min(np.median(c), (np.sum(c) + b) // n)
    ans = sum([abs(i - x) for i in c])
    print(ans)


if __name__ == "__main__":
    main()