import java.util.*;
import java.lang.*;
public class Main{
	public static void main(String [] args){
		Scanner in = new Scanner(System.in);
		double l = in.nextInt();
		double a  = l/3;
		l = l-a;
		double b = l/2;
		double c = (l-b);
		System.out.print(a*b*c);
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz