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 n) {
        long z=0;
        long z1=0;
        long max1=0;
       for(int i=0;i<n-1;i++){
           z=0;
           z1=0;
           for(int i1=i;i1<n;i1++){
          z=z+A[i1]*A[i1];
           z1=z1+(A[i1]);
            long r=(z1*z1-z)/2;
           if(r>max1)
             max1=r; 
        }
                   
        }
     
           
        return max1 ;
        
        
    }

    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,n);
        System.out.println(result);
        in.close();
    }
}