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

ll maxSubArraySum(ll a[], int size)
{
   ll max_so_far = a[0];
   ll curr_max = a[0];
   for (int i = 1; i < size; i++)
   {
        curr_max = max(a[i], curr_max+a[i]);
        max_so_far = max(max_so_far, curr_max);
   }
   return max_so_far;
}

int main() {
    int n;
    cin>>n;
    ll a[n], arr[n], maxsofar = 0, currmax = 0;
    for(int i = 0; i<n; arr[i++] = 0);
    for(int i = 0; i<n; cin>>a[i++]);
    for(int i = 0; i<n; i++)
        for(int j = 0; j<i; j++)
            arr[i]+=(a[i]*a[j]);
    cout << maxSubArraySum(arr, n);
    return 0;
}