import java.util.Scanner;

public class Main {

	public static void main(String... nui) {
		Scanner sc = new Scanner(System.in);
		
		double l = sc.nextInt();
		
		System.out.println(l * l * l / 27);

	}

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

	public static void main(String... nui) {
		Scanner sc = new Scanner(System.in);
		
		double l = sc.nextInt();
		
		System.out.println(l * l * l / 27);

	}

} Main public static void main(String... nui) {
		Scanner sc = new Scanner(System.in);
		
		double l = sc.nextInt();
		
		System.out.println(l * l * l / 27);

	} main {
		Scanner sc = new Scanner(System.in);
		
		double l = sc.nextInt();
		
		System.out.println(l * l * l / 27);

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double l = sc.nextInt(); l sc.nextInt() sc.nextInt sc System.out.println(l * l * l / 27) System.out.println System.out System System.out l * l * l / 27 l * l * l l * l * l l l l 27 String... nui nui public class Main {

	public static void main(String... nui) {
		Scanner sc = new Scanner(System.in);
		
		double l = sc.nextInt();
		
		System.out.println(l * l * l / 27);

	}

} public class Main {

	public static void main(String... nui) {
		Scanner sc = new Scanner(System.in);
		
		double l = sc.nextInt();
		
		System.out.println(l * l * l / 27);

	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String... nui) {
		Scanner sc = new Scanner(System.in);
		
		double l = sc.nextInt();
		
		System.out.println(l * l * l / 27);

	}

}