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

public class Solution {

    public static void main(String[] args) {
	// write your code here
        Scanner scanner = new Scanner(System.in);
        long k = scanner.nextLong();
        scanner.close();
        long solution = solve(k);
        System.out.println(solution);
    }

    public static long solve(long k) {
        long a = k * (k-1) + 1;
        long b = k * (k+1) - 1;
        long sum = (a + b) * k /2;
        return sum;
    }
}