import java.io.*;
import java.util.*;

class Main {
	
	public static void out (Object o) {
		System.out.println(o);
	}
	
	public static int solve (int d) {
		if (d < 4) return 0;
		if (d % 2 == 1) d--;
		
		d /= 2;
		boolean b = d % 2 == 0;
		d /= 2;
		return b ? d * d : d * (d + 1);
	}
	
	public static void main (String[] args) throws IOException {
		BufferedReader br = 
			new BufferedReader(new InputStreamReader(System.in));
		
		int d = Integer.parseInt(br.readLine());
		
		out(solve(d));
	}
}