using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static long largestValue(int[] A) {
        // Return the largest value of any of A's nonempty subarrays.
        int total = 0;
        int start =0;
        int end = A.Count()-1;
        for(int i = 0;i<A.Count();i++)
        {
            total += A[i];
        }
        //Console.WriteLine(total);
        for(int i = 0;i<A.Count();i++)
        {
            if(total < total - A[i])
            {
                start = i+1;
                total = total-A[i];
            }
            else
            {
                break;
            }
        }
        //Console.WriteLine(start);
        for(int i = A.Count()-1;i>0;i--)
        {
            if(total < total - A[i])
            {
                end = i-1;
                total = total-A[i];
            }
            else
            {
                break;
            }
        }
        //Console.WriteLine(end);
        int sumvalue =0;
        for(int i = start;i<end;i++)
        {
            for(int b=i+1;b<=end;b++)
            {
                sumvalue += A[b]*A[i];
            }
        }
        return sumvalue;
    }

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        string[] A_temp = Console.ReadLine().Split(' ');
        int[] A = Array.ConvertAll(A_temp,Int32.Parse);
        long result = largestValue(A);
        Console.WriteLine(result);
    }
}