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.
        double numberOfOdd1 = (Math.pow(k,2)+k)/2;
        long numberOfOdd = (long) numberOfOdd1;
        long sumOfK = 0;
        for (int i = 1; i < k+1; i++){
            sumOfK += 2*(numberOfOdd-i) + 1;
        }
        return sumOfK;
    }
    

    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();
    }
}