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

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long sum = 0;
        long sumUpK = 0;
        
        for (int i = 1; i < k; i++)
            sumUpK += i;
        for (long j = 2*sumUpK+1, p = 1; p <= k; p++, j += 2)
            sum += j;
        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();
    }
}