#include <bits/stdc++.h>

using namespace std;

long valueBetween(vector<int> A, int a, int b){
    long sum = A[b];
    long sum_tot = 0;
    for(int i = b-1; i >= a; i--){
        sum_tot += sum*A[i];
        sum += A[i];
    }   
    return sum_tot;
}

long largestValue(vector <int> A) {
    // Return the largest value of any of A's nonempty subarrays.
    long best = 0;
    for(int i = 0; i < A.size()-1; i++){
        for(int j = 1; j<A.size(); j++){
            long n = valueBetween(A,i,j);
            
            if(n > best)
                best = n;
        }
    }
    return best;
}


int main() {
    int n;
    cin >> n;
    vector<int> A(n);
    for(int A_i = 0; A_i < n; A_i++){
       cin >> A[A_i];
    }
    long result = largestValue(A);
    cout << result << endl;
    return 0;
}