#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
int MOD = 1e9+7;
main(){
    ll B,N;
    cin >> B >> N;
    vector<ll> V(N);
    ll sum = 0;
    rep(i,0,N){
        cin >> V[i];
        sum += V[i];
    }
    sort(V.begin(), V.end());
    ll level = min((V[N/2] + V[(N-1)/2]) / 2 , (sum + B) / N);
    ll ans = 0;
    rep(i,0,N){
        ans += abs(level - V[i]);
    }
    cout << ans << endl;
}