#!/usr/bin/env python
#coding:utf8

def read():
    B = input()
    
    C = []
    for i in range(input()):
        C.append(input())
    
    return B, C


def calc(num, C):
    ret = 0
    for i in range(len(C)):
        ret += abs(C[i] - num)
    return ret


def work((B, C)):
    L = 0
    R = (B + sum(C)) / len(C)

    while L + 10 < R:
        LL = L + (R - L) / 3
        RR = R - (R - L) / 3

        if calc(LL, C) < calc(RR, C):
            R = RR
        else:
            L = LL

    minV = 1 << 60
    for i in range(L, R + 1):
        minV = min(minV, calc(i, C))
    print minV


if __name__ == "__main__":
    work(read())