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 r=0,i,j,max,s,max1=0;
        int n=A.length;
        for(i=0;i<n;i++)
        {
            int a[]=new int[100000000];
            a[r++]=A[i];
            for(j=i+1;j<n;j++)
            {
                a[r++]=A[j];
                max=product(a,r);
                if(max>max1)
                    max1=max;
            }
        }
        return max1;
        // Return the largest value of any of A's nonempty subarrays.
    }
    public static int product(int[] a,int r)
    {
        int s=0,i,j,max=0,sum=0;
        int b[]=new int[10000000];
        for(i=0;i<r;i++)
        {
            for(j=i+1;j<r;j++)
            {
                b[s++]=a[i]*a[j];
            }
        }
        for(i=0;i<s;i++)
        {
            sum=sum+b[i];
        }
        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();
    }
}