import java.math.BigInteger;
import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        if(n<4){
        	System.out.println(0);
        	return;
        }
        int ans=0;
        for(int i=1;i<=n/4;i++){
        	ans=Math.max(ans, i*(n/2-i));
        }
        System.out.println(ans);
    }
}