import java.util.Scanner;
public class Main
{
    public static void main(String[] args) {
        Scanner a = new Scanner(System.in);
        int x = a.nextInt();
        //String x1 = a.nextLine();
        int y = 0;
        int z = 0;
        int [] array1 = new int[x];
        for(int i=0;i<x;i++)
        {
            array1[i] = a.nextInt();
            y+=array1[i];

            if(i==1 && array1[i] < array1[i-1] )
                {
                    int tmp = array1[i];
                    array1[i] = array1[i-1];
                    array1[i-1] = tmp;
                }
        }

        for(int i=array1.length-1;i>-1;i--)
        {
            z+=array1[i]*y;
            y-=array1[i];
            z+=array1[i]*y;
        }

        System.out.println(z);
    }
}