import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int l = scan.nextInt();

		scan.close();
		double ans = Math.pow((double)l/3,3);
		System.out.println(ans);
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int l = scan.nextInt();

		scan.close();
		double ans = Math.pow((double)l/3,3);
		System.out.println(ans);
	}
} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int l = scan.nextInt();

		scan.close();
		double ans = Math.pow((double)l/3,3);
		System.out.println(ans);
	} main {
		Scanner scan = new Scanner(System.in);
		int l = scan.nextInt();

		scan.close();
		double ans = Math.pow((double)l/3,3);
		System.out.println(ans);
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int l = scan.nextInt(); l scan.nextInt() scan.nextInt scan scan.close() scan.close scan double ans = Math.pow((double)l/3,3); ans Math.pow((double)l/3,3) Math.pow Math (double)l/3 (double)l 3 3 System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int l = scan.nextInt();

		scan.close();
		double ans = Math.pow((double)l/3,3);
		System.out.println(ans);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int l = scan.nextInt();

		scan.close();
		double ans = Math.pow((double)l/3,3);
		System.out.println(ans);
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int l = scan.nextInt();

		scan.close();
		double ans = Math.pow((double)l/3,3);
		System.out.println(ans);
	}
}
