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 numbers = k;

        long tmp = 0;
        for (; k > 0; k--) {
            tmp += k;
        }

        tmp = tmp * 2;


        long answer = 0;
        for (long i=tmp; numbers > 0; i--) {
            if (i % 2 != 0) {
                answer += i;
                numbers--;
            }
        }

        return answer;
    }

    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();
    }
}