#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
int n;
const int MAXN = 5 * 100000 + 2;
ll a[MAXN];
ll sum[MAXN];
ll sum2[MAXN];
int main () {
  ios::sync_with_stdio(false);
  cin >> n;
  for(int i = 0; i < n; ++i) {
    cin >> a[i];
    sum[i + 1] = sum[i] + a[i];
    sum2[i + 1] = sum2[i] + a[i] * a[i];
  }
  ll ret = 0;
  for(int i = 0; i < n; ++i) {
    for(int j = i + 1; j <= n; ++j) {
      ll cc = (sum[j] - sum[i]) * (sum[j] - sum[i]) - (sum2[j] - sum2[i]);
      cc /= 2;
      ret = max(cc, ret);
    }
  }
  cout << ret << endl;
}