import java.util.Scanner;

/**
 * @Author: 
 * @Date: 2023/3/2 1:04
 */
public class Main {
        public static void main(String[] args) {
            Scanner scanner = new Scanner(System.in);
            int k = scanner.nextInt(); //表示发放金币的天数
            int jb = 0; //总金币数
            int count = 1; //要发金币数
            for (int i = 0; i <= k ; i++) {
                k = k - count; //1 22 333
                for (int j = 0; j <= i ; j++) {
                    jb = jb + count;
                }
                count++;
            }
            System.out.println(jb);
        }
}