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.
        long startPoint = 0;
        for (long i = 1 ; i < k; i++) {
            startPoint += i;
        }
        startPoint = (startPoint * 2) + 1;
        long middle = (startPoint + (startPoint + (k - 1) * 2)) / 2;
        return middle * 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();
    }
}