#include<bits/stdc++.h>
#define int long long
using namespace std;
int n, a[100005], cnt, m, ans;
signed main() {
	cin >> m >> n;
	for(int i = 1;i <= n;i ++) {
		cin >> a[i];
		cnt += a[i];
	}
	cnt = cnt - m;
	for(int i = 1;i <= m;i ++) {
		if(i * n >= cnt) {
			ans = (i - 1) * (i - 1) * (i * n - cnt) + i * i * (n - (i * n - cnt));
			cout << ans;
			return 0;
		}
	}
	return 0;
}