import java.util.Scanner;
public class Yukicoder80 {
	public static void main(String[] args) {
		int D = new Scanner(System.in).nextInt(), max = 0;
		for (int i = 1; i < D/2; i ++) 	max = Math.max(max, i * (int)Math.floor((D - i * 2)/2));
		System.out.println(max);
	}
}