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

public class Solution {

    static long largestValue(int[] A) { 
        int m=0; int sum=0;int k=0;
        int b[]=new int[50];
        // Return the largest value of any of A's nonempty subarrays.
        for(int i=0;i<A.length;i++){
            for(int j=i+1;j<A.length;j++){
               b[k]=(A[i]*A[j]);  
                k++; 
        }
            }
        for (int j = 0; j < b.length; j++)
        {
        sum = sum + b[j];

        if (sum > m)
            m = sum ;
        else if (sum < 0)
            sum = 0;
        }
   
       return m;
    }

    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();
    }
}