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

public class Solution {
static int end=0,begin=0;
    static long largestValue(int[] A) {
        int m=maxSubArraySum(A);
        long max=0l;
        for(int i=begin;i<end;i++){
            for(int j=i+1;j<=end;j++)
                max+=A[i]*A[j];
        }
        //System.out.println(begin+" "+end);
        return max;
    }
    static int maxSubArraySum(int a[])
    {
        int size = a.length;
        int max_so_far = Integer.MIN_VALUE, max_ending_here = 0;
        boolean b=false;
        for (int i = 0; i < size; i++)
        {
            max_ending_here = max_ending_here + a[i];
            if (max_so_far < max_ending_here && !b){
                max_so_far = max_ending_here;
                begin=i;
                end=i;
                b=true;
            }
            if (max_so_far < max_ending_here && b){
                max_so_far = max_ending_here;
                end=i;
            }
            if (max_ending_here < 0){
                max_ending_here = 0;
                b=false;
            }
        }
        return max_so_far;
    }
    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();
    }
}