import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
//		int b = sc.nextInt();
		double res = 0;
//		String s = sc.next();
//		String res = "";

		double da = a;

		res = (da/3)*(da/3)*(da/3);
		System.out.printf("%f", res);
		//System.out.println(res);
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
//		int b = sc.nextInt();
		double res = 0;
//		String s = sc.next();
//		String res = "";

		double da = a;

		res = (da/3)*(da/3)*(da/3);
		System.out.printf("%f", res);
		//System.out.println(res);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
//		int b = sc.nextInt();
		double res = 0;
//		String s = sc.next();
//		String res = "";

		double da = a;

		res = (da/3)*(da/3)*(da/3);
		System.out.printf("%f", res);
		//System.out.println(res);
	} main {
		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
//		int b = sc.nextInt();
		double res = 0;
//		String s = sc.next();
//		String res = "";

		double da = a;

		res = (da/3)*(da/3)*(da/3);
		System.out.printf("%f", res);
		//System.out.println(res);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc double res = 0; res 0 double da = a; da a res = (da/3)*(da/3)*(da/3) res (da/3)*(da/3)*(da/3) (da/3)*(da/3)*(da/3) (da/3) da 3 (da/3) da 3 (da/3) da 3 System.out.printf("%f", res) System.out.printf System.out System System.out "%f" res String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
//		int b = sc.nextInt();
		double res = 0;
//		String s = sc.next();
//		String res = "";

		double da = a;

		res = (da/3)*(da/3)*(da/3);
		System.out.printf("%f", res);
		//System.out.println(res);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
//		int b = sc.nextInt();
		double res = 0;
//		String s = sc.next();
//		String res = "";

		double da = a;

		res = (da/3)*(da/3)*(da/3);
		System.out.printf("%f", res);
		//System.out.println(res);
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int a = sc.nextInt();
//		int b = sc.nextInt();
		double res = 0;
//		String s = sc.next();
//		String res = "";

		double da = a;

		res = (da/3)*(da/3)*(da/3);
		System.out.printf("%f", res);
		//System.out.println(res);
	}
}
