#include <iostream>
#include <vector>
#include <cmath>
#include <numeric>

#define REP(i, n) for(int i=0;i<(n);i++)

using namespace std;


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    long B, N;
    cin >> B >> N;
    vector<long> C;
    REP(i,N) {
        long c;
        cin >> c;
        C.push_back(c);
    }

     long long l = 0, r = 1000000000000000000;
    while (r - l > 2) {
         long long lm, rm;
        lm = (l + r) / 3;
        rm = (l + r) / 3 * 2;
        if (lm * N - accumulate(C.begin(), C.end(), 0) > B) {
            r = lm;
        } else if (rm * N - accumulate(C.begin(), C.end(), 0) > B) {
            r = rm;
        } else if (accumulate(C.begin(), C.end(), 0, [lm]( long long acc,  long long c) { return acc + abs(c - lm); }) >=
                accumulate(C.begin(), C.end(), 0, [rm]( long long acc,  long long c) { return acc + abs(c - rm); })) {
            r = rm;
        } else {
            l = lm;
        }
    }
    cout << accumulate(C.cbegin(), C.cend(), 0, [r, l]( long long acc,  long long c) { return acc + abs((r + l) / 2 - c); }) << endl;

    return 0;
}