// No.198 キャンディー・ボックス２
// https://yukicoder.me/problems/no/198
//
#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <utility>
using namespace std;

long long int solve(unsigned int B, unsigned int N, vector<int>& candies);
long long calc_cost(long long  n, vector<int>& candies);


int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    unsigned int B, N;
    cin >> B >> N;
    vector<int> candies(N);
    for (int i = 0; i < N; ++i)
        cin >> candies[i];

    long long ans = solve(B, N, candies);
    cout << ans << endl;
}


long long int solve(unsigned int B, unsigned int N, vector<int>& candies) {
    sort(candies.begin(), candies.end());

    long long  median;
    if (N % 2 == 1)
        median = candies[N/2];
    else
        median = (candies[(N-1)/2] + candies[N/2]) / 2;

    long long max_avg = B;
    for (auto c: candies)
        max_avg += c;
    max_avg /= N;
    median = min(median, max_avg);

    long long ans = calc_cost(median, candies);
    return ans;
}


long long calc_cost(long long  n, vector<int>& candies) {
    long long ans = 0;
    for (auto s: candies) {
        ans += abs(s - n);
    }
    return ans;
}