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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    std::cin>>n;
    std::vector<long long> a(n);
    for(int i=0;i<n;++i){
        std::cin>>a[i];
    }
    long long res=0;
    for(int i=1;i<n;++i){
        long long prosum=0,sum=a[i-1];
        for(int j=i;j<n;++j){
            prosum+=a[j]*sum;
            sum+=a[j];
            res=std::max(res,prosum);
        }
    }
    std::cout<<res<<std::endl;
    return 0;
}