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

public class Solution {

    static long sumOfGroup(long k) {
        long  a = k * k;
        a  = a - k + 1;
        long odd = a;
        long sum = odd;
        for(int i = 0; i < k - 1; i++) {
            odd += 2;
            sum += odd;
        }
        return sum;
    }

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