#include <iostream>
#include <cstdio>

using namespace std;

int V[500004];

int main() {
//    #ifndef ONLINE_JUDGE
//    freopen("input.txt","r",stdin);
//    #endif // ONLINE_JUDGE

    int N;
    scanf("%d\n", &N);

    for(int i = 1; i <= N; ++i) {
        scanf("%d", &V[i]);
    }

    int ans = 0;
    for(int i = 1; i <= N; ++i) {
        int S = V[i];
        int beauty = 0;

        for(int j = i + 1; j <= N; ++j) {
            beauty += S * V[j];
            S += V[j];
            ans = max(ans, beauty);
        }
    }

    cout << ans << '\n';

    return 0;
}