#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
    ll B, N;
    cin >> B >> N;
    vector<ll> C(N);
    for (int i = 0; i < N; i++) {
        cin >> C[i];
    }

    auto cost = [&](ll n) {
        ll ret = 0;
        for (int i = 0; i < N; i++) {
            ret += abs(C[i] - n);
        }
        return ret;
    };

    ll l = *min_element(C.begin(), C.end()), r = (accumulate(C.begin(), C.end(), 0ll) + B) / N + 1;
    while (r - l > 3) {
        ll ml = (l * 2 + r) / 3, mr = (l + r * 2) / 3;
        if (cost(ml) < cost(mr))
            r = mr;
        else
            l = ml;
    }

    ll ans = cost(l);
    for (ll i = l; i < r; i++) {
        ans = min(ans, cost(i));
    }

    cout << ans << endl;
}