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.
        int i,j,n=A.length;
        long ans=-1000007,curr;
        long csum[]=new long[n+1];
        long sqsum[]=new long[n+1];
        for(i=0;i<n;i++){
            csum[i+1]=csum[i]+A[i];
            sqsum[i+1]=sqsum[i]+(long)A[i]*A[i];
        }
        for(i=0;i<n;i++){
            for(j=0;j<i;j++){
                curr=csum[i+1]-csum[j];
                curr=(curr*curr-sqsum[i+1]+sqsum[j])/2;
                ans=Math.max(curr,ans);
            }
        }
        return ans;
    }

    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();
    }
}