import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		System.out.println((n * n * n) / 27.0);
		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 n = sc.nextInt();
		System.out.println((n * n * n) / 27.0);
		sc.close();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		System.out.println((n * n * n) / 27.0);
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		System.out.println((n * n * n) / 27.0);
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc System.out.println((n * n * n) / 27.0) System.out.println System.out System System.out (n * n * n) / 27.0 (n * n * n) n * n * n n n n 27.0 sc.close() sc.close sc String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		System.out.println((n * n * n) / 27.0);
		sc.close();
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		System.out.println((n * n * n) / 27.0);
		sc.close();
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		System.out.println((n * n * n) / 27.0);
		sc.close();
	}
}
