import java.util.Scanner;

public class Task3
{
    public static void main(String[] args)
    {
       Scanner sc = new Scanner(System.in);
       int num = sc.nextInt();
       int result = 0;
       for (int i = 1; i <= num; i++)
       {
           for (int j = 1; j <= i; j++)
           {
               result +=j;
           }
       }
       System.out.print(result);
    }
}