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

public class Solution {

    static long largestValue(int[] A) {
        
        long s = 0; int f = 0, st = 0, ed = 0;
        
        for(int i = 0; i < A.length; i++)
        {
            if(A[i] < 0 && f == 0)
                continue;
            else if(A[i] > 0 && f == 0)
            {
                st = i;
                f = 1;
            }
            else
            {
                for(int j = A.length - 1; j > A[i]; j--)
                {
                    if(A[j] < 0)
                        continue;
                    ed = j;
                    break;
                }
            }
                
        }
        
        for(int i = st; i < ed; i++)
        {
           for(int j = i+1; j <= ed; j++)
           {
               s = s + (A[i] * A[j]);
           }
        }
        
        return s;
        
    }

    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();
    }
}