import java.io.*;
import java.util.*;

public class Solution {

    private static PrintWriter out;

    public static void main(String[] args) throws Exception {
        out = new PrintWriter(System.out);
        new Solution().solve();
        out.close();
    }

    private BufferedReader reader;
    private StringTokenizer st;

    private long sum = 0L;
    private int k;

    private void solve() throws Exception {

        reader = new BufferedReader(new InputStreamReader(System.in));
        k = Integer.parseInt(reader.readLine());
        reader.close();

        long first = 1;
        long last = 1;
        for (int i = 2; i <= k; ++i) {
            first = last + 2;
            last = first + 2 * (i - 1);
        }

        sum = ((first + last) * k) / 2;

        out.println(sum);
    }
}