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

public class Solution {

    static long sumOfGroup(int k) {
        if (k == 1) {
            return 1;
        }

        long sOfK = (long)k * (k - 1) / 2;

        long start = 2 * sOfK + 1;

        long sum = 0;
        for (int i = 0; i < k; i++) {
            sum += start + 2 * i;
        }

        return sum;
    }

    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();
    }
}