#include <bits/stdc++.h>
using namespace std;
#define fastcin {\
    cin.tie(0);\
    ios::sync_with_stdio(false);\
}
#define rep(i, a, b) for(int i = a; i < b; i++)
#define print(x) cout << x << "\n"
#define VSORT(v) sort(v.begin(), v.end());
typedef long long ll;
typedef vector<ll> vll;
const ll infl = 1e18+7;

int main() {
    fastcin;
    ll b, n, in, mid, sum, ck = 0, ans = 0;
    cin >> b >> n;
    sum = b;
    vll c;
    rep(i, 0, n) {
        cin >> in;
        sum += in;
        c.push_back(in);
    }
    VSORT(c);
    mid = c[n/2];
    rep(i, 0, n/2) ans += mid-c[i];
    rep(i, n/2, n) ck += c[i]-mid;
    if(ck+b>=ans) ans += ck;
    else {
        ans = 0;
        ll avg = sum/n;
        rep(i, 0, n) ans += abs(avg-c[i]);
    }
    print(ans);
    return 0;
}