#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    ll B,N; cin >> B >> N;
    vector<ll> C(N);
    rep(i,N) cin >> C[i];

    sort(C.begin(), C.end());
    ll X = C[N / 2], sumC = accumulate(C.begin(), C.end(), 0LL);
    if(B + sumC < X * N) X = (B + sumC) / N; // 足りない場合
    ll ans = 0;
    rep(i,N) ans += abs(X - C[i]);
    cout << ans << endl;
}