import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = Integer.parseInt(sc.next());
		double edge = L / 3.0;
		double ans = edge * edge * edge;
		System.out.printf("%.12f\n", ans);
	}

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

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = Integer.parseInt(sc.next());
		double edge = L / 3.0;
		double ans = edge * edge * edge;
		System.out.printf("%.12f\n", ans);
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = Integer.parseInt(sc.next());
		double edge = L / 3.0;
		double ans = edge * edge * edge;
		System.out.printf("%.12f\n", ans);
	} main {
		Scanner sc = new Scanner(System.in);
		int L = Integer.parseInt(sc.next());
		double edge = L / 3.0;
		double ans = edge * edge * edge;
		System.out.printf("%.12f\n", ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int L = Integer.parseInt(sc.next()); L Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc double edge = L / 3.0; edge L / 3.0 L 3.0 double ans = edge * edge * edge; ans edge * edge * edge edge * edge * edge edge edge edge System.out.printf("%.12f\n", ans) System.out.printf System.out System System.out "%.12f\n" ans String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = Integer.parseInt(sc.next());
		double edge = L / 3.0;
		double ans = edge * edge * edge;
		System.out.printf("%.12f\n", ans);
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = Integer.parseInt(sc.next());
		double edge = L / 3.0;
		double ans = edge * edge * edge;
		System.out.printf("%.12f\n", ans);
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = Integer.parseInt(sc.next());
		double edge = L / 3.0;
		double ans = edge * edge * edge;
		System.out.printf("%.12f\n", ans);
	}

}
