import java.util.ArrayDeque;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		sc.close();

		if (n == 1) {
			System.out.println(0);
			return;
		}

		ArrayDeque<Long> que = new ArrayDeque<Long>();
		que.add(1L);
		long left = 2;
		long right = n;
		while (left <= right) {
			que.addFirst(right);
			right--;
			if (left <= right) {
				que.addLast(right);
				right--;
			}
			if (left <= right) {
				que.addFirst(left);
				left++;
			}
			if (left <= right) {
				que.addLast(left);
				left++;
			}
		}

		long ans = 0;
		long first = que.pollFirst();
		long i = 0;
		long j = first;
		while (!que.isEmpty()) {
			i = j;
			j = que.pollFirst();
			ans += i * j + j - i;
		}
		ans += j * first + first - j;
		System.out.println(ans);
	}
}