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

public class Solution {

    static long sumOfGroup(int k) {
        long l = k;
        return l*f((int)l) + (l-1)*l;
    }

    private static long f(int k) {
        return k == 0 ? 1 : f(k-1) + (k-1)*2;
    }


    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();
    }
}