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 currentOdd = -1;
        long sum = 0;
        if (k == 0) {
            return 0;
        }

        for (long i = 0; i < k; i++) {
            if (i == k -1) {

                for (long j = 0; j < k; j++) {
                    currentOdd +=2;
                    sum += currentOdd;
                }
                return sum;
            } else {
                if (currentOdd > 0) currentOdd += (i  + 1) * 2;
                else currentOdd +=2;
            }
        }
        return sum;
    }


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