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

public class Solution {

    static long sumOfGroup(int k) {
        if (k == 1) {
            return 1;
        }
        long x = sum(1l, 1, k - 1);
        long a = 1 + x * 2;
        return sum(a, 2, k);
    }

    static long sum(long a, int k, int n) {
        long b = a + k * (n - 1);
        return (a + b) * n / 2;
    }

    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();
    }
}