#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <numeric>
#define rep(x, to) for (int x = 0; x < (to); x++)
#define REP(x, a, to) for (int x = (a); x < (to); x++)
#define foreach(itr, x) for (typeof((x).begin()) itr = (x).begin(); itr != (x).end(); itr++)

using namespace std;

typedef long long ll;
typedef pair<int, int> PII;
typedef pair<long, long> PLL;

ll B, N;
ll c[15];
ll mx; //均一化できる最大数
const ll INF = (ll)(1e+18 + 7);

ll f(ll x) {
	ll cost = 0;
	ll have = B;
	//箱のキャンディをx個にするときの作業数
	rep(i, N) {
		have += c[i] - x;
		cost += abs(c[i] - x);
	}
	if (have < 0) cost = INF;
	return cost;
}

void solve() {
	ll left = 0;
	ll right = mx;
	while (right - left > 2) {
		ll a = (2 * left + right) / 3;
		ll b = (left + 2 * right) / 3;
		if (f(a) < f(b)) {
			right = b;
		} else {
			left = a;
		}
	}
	cout << min(f(left), min(f(left+1), f(right))) << endl;
}

int main() {
	cin >> B;
	cin >> N;
	rep(i, N) {
		cin >> c[i];
	}

	rep(i, N) mx += c[i];
	mx += B;
	mx /= N;

	solve();

	return 0;
}