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 kLong = k; 
		long firstElemKthGroupPos = 1 + kLong * (kLong- 1) / 2;
		long firstElemKthGroup = 1 + (firstElemKthGroupPos - 1) * 2;

		long sum = 0;
		for (int i = 0; i < k; i++) {
			sum = sum + (firstElemKthGroup + 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();
    }
}