import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		if (n == 1) {
		    System.out.println(0);
		    return;
		} else if (n == 2) {
		    System.out.println(4);
		    return;
		}
		long total = n + n - 1;
		long left = 2;
		long right = n;
		if (n % 2 == 1) {
    		while (right - left > 1) {
    		    total += left * right + left * (right - 2);
    		    left++;
    		    right--;
    		}
    		total += left * right;
		} else {
		    while (right - left > 2) {
    		    total += left * right + left * (right - 2);
    		    left++;
    		    right--;
		    }
		    total += left * right + left * (right - 1);
		}
		System.out.println(total);
	}
}