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

public class Solution {
    
    static int SumOfProducts(int[] arr, int l){
        int output = 0;
        if(l==0){
            System.out.print(arr[0] + " ");
            return arr[0];   
        }
        for(int i=0; i<l; i++){
            for(int j=i+1; j<l; j++){
                output += arr[i] * arr[j];
            }
        }    
        return output;
    }

    static int largestValue(int[] A) {
        int sumSubarray = Integer.MIN_VALUE;
        int f=A[0];
        sumSubarray = f;
        for(int j=1; j<A.length; j++){
           f = Math.max(f, SumOfProducts(A, j));
           sumSubarray = Math.max(sumSubarray, f);
        }
        return sumSubarray;
    }

    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();
        }
        int result = largestValue(A);
        System.out.println(result);
        in.close();
    }
}