#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <fstream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

ll f(ll B, int N, vector<ll>& C, ll c) {
	ll b = B, sum = 0;
	for (int i = 0; i < N; i++)
		if (C[i] > c) {
			b += C[i] - c;
			sum += C[i] - c;
		}
	bool ok = true;
	for (int i = 0; i < N; i++)
		if (C[i] < c) {
			if (b >= c - C[i]) {
				b -= c - C[i];
				sum += c - C[i];
			}
			else ok = false;
		}
	return ok ? sum : LLONG_MAX;
}

int main() {
	ll B; cin >> B;
	int N; cin >> N;
	vector<ll> C(N);
	ll sum = B;
	for (int i = 0; i < N; i++) {
		cin >> C[i];
		sum += C[i];
	}
	ll mini = f(B, N, C, sum / N);
	for (int i = 0; i < N; i++)
		mini = min(mini, f(B, N, C, C[i]));
	cout << mini << endl;
}