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

public class Solution {

    static long largestValue(int[] arr,int n) {
        // Return the largest value of any of A's nonempty subarrays.
       // Arrays.sort(A);
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<n-1-i;j++)
            {
                if(Math.abs(arr[j])>Math.abs(arr[j+1]))
                {
                    int temp=arr[j];
                    arr[j]=arr[j+1];
                    arr[j+1]=temp;
                }
            }
        }
       // System.out.println(Arrays.toString(arr));
         List<Integer> val=new ArrayList<Integer>();
         for(int i=n-1;i>=0;i--)
        {
             
           
            if(val.size()==0||Math.abs(val.get(val.size()-1))!=Math.abs(arr[i]))
                val.add(arr[i]);
        }
        n=val.size();
       /* for(int i=0;i<n;i++)
            System.out.print(val.get(i)+"  ");*/
        long sum=0;
        for(int i=0;i<n-1;i++)
        {
            for(int j=i+1;j<n;j++)
                sum+=(long)(val.get(i)*val.get(j));
        }
        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,n);
        System.out.println(result);
        in.close();
    }
}