import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int m = sc.nextInt();
		double n =m;

		String ans = "Yes";
		sc.close();
		System.out.println((n/3)*(n/3)*(n/3));
	}
} import java.util.Scanner; Scanner java.util public class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int m = sc.nextInt();
		double n =m;

		String ans = "Yes";
		sc.close();
		System.out.println((n/3)*(n/3)*(n/3));
	}
} Main public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int m = sc.nextInt();
		double n =m;

		String ans = "Yes";
		sc.close();
		System.out.println((n/3)*(n/3)*(n/3));
	} main {
		Scanner sc = new Scanner(System.in);
		int m = sc.nextInt();
		double n =m;

		String ans = "Yes";
		sc.close();
		System.out.println((n/3)*(n/3)*(n/3));
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int m = sc.nextInt(); m sc.nextInt() sc.nextInt sc double n =m; n m String ans = "Yes"; ans "Yes" sc.close() sc.close sc System.out.println((n/3)*(n/3)*(n/3)) System.out.println System.out System System.out (n/3)*(n/3)*(n/3) (n/3)*(n/3)*(n/3) (n/3) n 3 (n/3) n 3 (n/3) n 3 String[] args args public class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int m = sc.nextInt();
		double n =m;

		String ans = "Yes";
		sc.close();
		System.out.println((n/3)*(n/3)*(n/3));
	}
} public class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int m = sc.nextInt();
		double n =m;

		String ans = "Yes";
		sc.close();
		System.out.println((n/3)*(n/3)*(n/3));
	}
} Main
import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		int m = sc.nextInt();
		double n =m;

		String ans = "Yes";
		sc.close();
		System.out.println((n/3)*(n/3)*(n/3));
	}
}
