#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#define ll long long
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin >> n;
    vector <ll> vec(n);
    for(int i = 0; i < n; i++) cin >> vec[i];
    ll sum = 0;
    ll ans = 0;
    for(int i = 0; i < n-1; i++){
        sum = 0;
        sum += vec[i];
        ll prod = 1;
        ll sum1 = 0;
        for(int j = i+1; j < n; j++){
            sum1 += sum*vec[j];
            ans = max(ans, sum1);
            //cout << i << " " << j << " " << sum << " " << sum1 << endl;
            sum += vec[j];
        }
    }
    cout << ans;
    return 0;
}