
import java.util.Scanner;

public class Main {
static Scanner s = new Scanner(System.in);
	public static void main(String[] args) {
		double l = s.nextDouble();
		
		double k = l/3;
		double v = Math.pow(l/3,3);
		System.out.println(v);
	}

}
//36926037.000000000000
/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