import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		int l = sc.nextInt();

		double part = (double)l / (double)3.0;
		
		double box = part * part * part;
		
		
		log( box );
		sc.close();
		
	}

	static void log(double d) {
		System.out.printf("%.12f\n",d);
	}

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

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		int l = sc.nextInt();

		double part = (double)l / (double)3.0;
		
		double box = part * part * part;
		
		
		log( box );
		sc.close();
		
	}

	static void log(double d) {
		System.out.printf("%.12f\n",d);
	}

} Main public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		int l = sc.nextInt();

		double part = (double)l / (double)3.0;
		
		double box = part * part * part;
		
		
		log( box );
		sc.close();
		
	} main {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		int l = sc.nextInt();

		double part = (double)l / (double)3.0;
		
		double box = part * part * part;
		
		
		log( box );
		sc.close();
		
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int l = sc.nextInt(); l sc.nextInt() sc.nextInt sc double part = (double)l / (double)3.0; part (double)l / (double)3.0 (double)l (double)3.0 double box = part * part * part; box part * part * part part * part * part part part part log( box ) log box sc.close() sc.close sc String[] args args static void log(double d) {
		System.out.printf("%.12f\n",d);
	} log {
		System.out.printf("%.12f\n",d);
	} System.out.printf("%.12f\n",d) System.out.printf System.out System System.out "%.12f\n" d double d d public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		int l = sc.nextInt();

		double part = (double)l / (double)3.0;
		
		double box = part * part * part;
		
		
		log( box );
		sc.close();
		
	}

	static void log(double d) {
		System.out.printf("%.12f\n",d);
	}

} public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		int l = sc.nextInt();

		double part = (double)l / (double)3.0;
		
		double box = part * part * part;
		
		
		log( box );
		sc.close();
		
	}

	static void log(double d) {
		System.out.printf("%.12f\n",d);
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		int l = sc.nextInt();

		double part = (double)l / (double)3.0;
		
		double box = part * part * part;
		
		
		log( box );
		sc.close();
		
	}

	static void log(double d) {
		System.out.printf("%.12f\n",d);
	}

}
