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

public class Solution {

    static long sumOfGroup(long k) {
        long poc, kraj, suma;
        poc = k*(k-1)/2;
        kraj = k*(k+1)/2-1;
        suma = kraj*(kraj+1)-poc*(poc-1)+kraj-poc+1;
        return suma;
        // Return the sum of the elements of the k'th group.
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        long answer = sumOfGroup((long)k);
        System.out.println(answer);
        in.close();
    }
}