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

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        /*
        const start = k * k - k + 1;
        const end = (k+1) * (k+1) - (k+1) -1;

        return (start + end) * k / 2;*/
        long k_ = (long) k;
        long start = k_ * k_ - k_ + 1;
        long end = (k_+1) * (k_+1) - (k_+1) -1;
        
        return ((start + end) / 2) * k_;
    }

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