import java.util.ArrayList;
import java.util.Scanner;

/**
 * Created by Tejas on 02-02-2018.
 */
public class PairSums {

    static long largestValue(int[] a) {

        long maximum=0;
        for (int i=0;i<=a.length-1;i++)
        {
            for (int j=i;j<=a.length-1;j++)
            {
                ArrayList<Integer> arrayList=new ArrayList<>();
                for (int k=i;k<=j;k++)
                {
                    arrayList.add(a[k]);
                }

                long res=getResult(arrayList);

                if (res>maximum)
                {
                    maximum=res;
                }
            }
        }
        return maximum;
    }

    static long getResult(ArrayList<Integer> a)
    {
        long sum=0;
        for (int i=0;i<=a.size()-2;i++)
        {
            for (int j=i+1;j<=a.size()-1;j++)
            {
                int num1=a.get(i);
                int num2=a.get(j);
                sum+=(num1*num2);
            }
        }
        return sum;
    }

    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();
    }
}