/* -*- coding: utf-8 -*-
 *
 * 198.cc: No.198 キャンディー・ボックス2 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 10;

/* typedef */

typedef long long ll;

/* global variables */

ll cs[MAX_N];

/* subroutines */

ll steps(int n, ll a) {
  ll d = 0;
  for (int i = 0; i < n; i++)
    d += (cs[i] > a) ? cs[i] - a : a - cs[i];
  return d;
}

/* main */

int main() {
  ll b;
  int n;
  cin >> b >> n;

  ll sum = 0;
  for (int i = 0; i < n; i++) {
    cin >> cs[i];
    sum += cs[i];
  }

  ll c0 = -1, c1 = (sum + b) / n;

  while (c0 + 2 < c1) {
    ll a0 = (c0 * 2 + c1) / 3;
    ll a1 = (c0 + c1 * 2) / 3;

    if (steps(n, a0) <= steps(n, a1)) c1 = a1;
    else c0 = a0;
  }
  //printf("steps(%lld)=%lld, steps(%lld)=%lld\n",
  //c0, steps(n, c0), c1, steps(n, c1));

  ll mins = steps(n, c0);
  ll s1 = steps(n, c0 + 1);
  ll s2 = steps(n, c0 + 2);
  if (mins > s1) mins = s1;
  if (mins > s2) mins = s2;
  printf("%lld\n", mins);
  return 0;
}