
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Main main = new Main();
		main.run();
	}

	public void run() {
		Scanner sc = new Scanner(System.in);
		double n = sc.nextLong();
		double l = n/3;
		System.out.printf("%.12f\n",Math.pow(l, 3));
		sc.close();
	}


} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Main main = new Main();
		main.run();
	}

	public void run() {
		Scanner sc = new Scanner(System.in);
		double n = sc.nextLong();
		double l = n/3;
		System.out.printf("%.12f\n",Math.pow(l, 3));
		sc.close();
	}


} Main public static void main(String[] args) {
		Main main = new Main();
		main.run();
	} main {
		Main main = new Main();
		main.run();
	} Main main = new Main(); main new Main() main.run() main.run main String[] args args public void run() {
		Scanner sc = new Scanner(System.in);
		double n = sc.nextLong();
		double l = n/3;
		System.out.printf("%.12f\n",Math.pow(l, 3));
		sc.close();
	} run {
		Scanner sc = new Scanner(System.in);
		double n = sc.nextLong();
		double l = n/3;
		System.out.printf("%.12f\n",Math.pow(l, 3));
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double n = sc.nextLong(); n sc.nextLong() sc.nextLong sc double l = n/3; l n/3 n 3 System.out.printf("%.12f\n",Math.pow(l, 3)) System.out.printf System.out System System.out "%.12f\n" Math.pow(l, 3) Math.pow Math l 3 sc.close() sc.close sc public class Main {

	public static void main(String[] args) {
		Main main = new Main();
		main.run();
	}

	public void run() {
		Scanner sc = new Scanner(System.in);
		double n = sc.nextLong();
		double l = n/3;
		System.out.printf("%.12f\n",Math.pow(l, 3));
		sc.close();
	}


} public class Main {

	public static void main(String[] args) {
		Main main = new Main();
		main.run();
	}

	public void run() {
		Scanner sc = new Scanner(System.in);
		double n = sc.nextLong();
		double l = n/3;
		System.out.printf("%.12f\n",Math.pow(l, 3));
		sc.close();
	}


} Main

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Main main = new Main();
		main.run();
	}

	public void run() {
		Scanner sc = new Scanner(System.in);
		double n = sc.nextLong();
		double l = n/3;
		System.out.printf("%.12f\n",Math.pow(l, 3));
		sc.close();
	}


}
