import java.util.Scanner;

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

		long n2 = (n + 1) / 2;
		long ans = n2 * (n2 + 1) / 2;
		System.out.println(ans);
	}
}