import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    
    static long productSum(int A[], int n , int a , int b)
    {
        int sum = 0;
        for (int i = a; i <= b; i++)
            sum = sum + A[i];


        int sum_square = sum * sum;

        int square_sum = 0;
        for (int i = a; i <= b; i++)
            square_sum += A[i]*A[i];

        return (sum_square - square_sum)/2;
    }

    static long largestValue(int[] A) {
        
        int i , j , n = A.length;
        long max = Integer.MIN_VALUE;
        for(i = 0; i < n-1; i++)
        {
            for(j = i+1; j < n; j++)
            {
                long sum = productSum(A , n , i , j);
                if(sum > max)
                    max = sum;
            }
        }
        return max;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] A = new int[n];
        for(int A_i = 0; A_i < n; A_i++){
            A[A_i] = in.nextInt();
        }
        long result = largestValue(A);
        System.out.println(result);
        in.close();
    }
}