import java.util.Scanner;

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long longk = (long) k;
        long constant = longk * (longk - 1);
        long begin = constant + 1;
        return (begin * longk) + constant;
    }

    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();
    }
}