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 max = int.MinValue;
        for (int i = 0; i < a.Length; i++){
            int sum = a[i];
            int prev = 0;
            int total = 0;
            for (int j = i + 1; j < a.Length; j++){
                total = prev + sum * a[j];
                prev = total;
                sum += a[j];
                max = Math.Max(max,total);
            }
            
        }
        return max;
    }

    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);
    }
}