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

public class Solution {

    static long largestValue(int[] A) {
        // Return the largest value of any of A's nonempty subarrays.
        long result = 0;
	      
		 int n = A.length;
	        // Pick starting point
	        for (int i = 0; i < n; i ++)
	        {
	            // Pick ending point
	            for (int j = i; j < n; j ++)
	            {
	                // sum subarray between current
	                // starting and ending points
	            	int size = j-i+1;
	            	int[] a = new int[size];
	            	int counter = 0 ;
	                for (int k = i; k <= j; k++) {
	                	a[counter] = A[k];
	                	
	                	counter++;
	                }
	              
	                long value = findValue(a);
	                if(value >= result) {
	                	result = value;
	                }
	            }
	        }
		 
		 return result;
    }
    
     
	 static long findValue(int[] a) {
	
		 int length = a.length;
		 long sum = 0;
		 for(int i = 0; i<length; i++) {
			 for(int j = i+1; j<length; j++) {
				 int product  = a[i] * a[j];
			
				 sum += product;
			 }
		 }
		 
		 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();
    }
}