import java.util.Scanner;

public class Main {

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

		System.out.println(Math.pow((double)len/3 , 3));

		sc.close();
	}
} import java.util.Scanner; Scanner java.util public class Main {

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

		System.out.println(Math.pow((double)len/3 , 3));

		sc.close();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		System.out.println(Math.pow((double)len/3 , 3));

		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		System.out.println(Math.pow((double)len/3 , 3));

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

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

		System.out.println(Math.pow((double)len/3 , 3));

		sc.close();
	}
} public class Main {

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

		System.out.println(Math.pow((double)len/3 , 3));

		sc.close();
	}
} Main
import java.util.Scanner;

public class Main {

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

		System.out.println(Math.pow((double)len/3 , 3));

		sc.close();
	}
}
