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

int main(){
    int B, N;
    cin >> B >> N;
    
    ll sum = B;

    vector<int> C(N);
    for(int i=0;i<N;i++){
        cin >> C[i];
        sum += C[i];
    }

    sort(C.begin(), C.end());

    int t = min((int)(sum / C.size()), C[C.size() / 2]);
    ll res = 0;

    for(int x : C){
        res += abs(x - t);
    }

    cout << res << endl;
    return 0;
}