import java.io.*;
import java.util.*;

public class Main extends PrintWriter {
	Main() { super(System.out, true); }
	Scanner sc = new Scanner(System.in);
	public static void main(String[] $) {
		Main o = new Main(); o.main(); o.flush();
	}

	void main() {
		int l = sc.nextInt();
		double a = l / 3.0;
		printf("%.6f\n", a * a * a);
	}
} import java.io.*; io.* java import java.util.*; util.* java public class Main extends PrintWriter {
	Main() { super(System.out, true); }
	Scanner sc = new Scanner(System.in);
	public static void main(String[] $) {
		Main o = new Main(); o.main(); o.flush();
	}

	void main() {
		int l = sc.nextInt();
		double a = l / 3.0;
		printf("%.6f\n", a * a * a);
	}
} Main Scanner sc = new Scanner(System.in); sc new Scanner(System.in) Main() { super(System.out, true); } Main { super(System.out, true); } super(System.out, true) super System.out System System.out true public static void main(String[] $) {
		Main o = new Main(); o.main(); o.flush();
	} main {
		Main o = new Main(); o.main(); o.flush();
	} Main o = new Main(); o new Main() o.main() o.main o o.flush() o.flush o String[] $ $ void main() {
		int l = sc.nextInt();
		double a = l / 3.0;
		printf("%.6f\n", a * a * a);
	} main {
		int l = sc.nextInt();
		double a = l / 3.0;
		printf("%.6f\n", a * a * a);
	} int l = sc.nextInt(); l sc.nextInt() sc.nextInt sc double a = l / 3.0; a l / 3.0 l 3.0 printf("%.6f\n", a * a * a) printf "%.6f\n" a * a * a a * a * a a a a PrintWriter public class Main extends PrintWriter {
	Main() { super(System.out, true); }
	Scanner sc = new Scanner(System.in);
	public static void main(String[] $) {
		Main o = new Main(); o.main(); o.flush();
	}

	void main() {
		int l = sc.nextInt();
		double a = l / 3.0;
		printf("%.6f\n", a * a * a);
	}
} public class Main extends PrintWriter {
	Main() { super(System.out, true); }
	Scanner sc = new Scanner(System.in);
	public static void main(String[] $) {
		Main o = new Main(); o.main(); o.flush();
	}

	void main() {
		int l = sc.nextInt();
		double a = l / 3.0;
		printf("%.6f\n", a * a * a);
	}
} Main
import java.io.*;
import java.util.*;

public class Main extends PrintWriter {
	Main() { super(System.out, true); }
	Scanner sc = new Scanner(System.in);
	public static void main(String[] $) {
		Main o = new Main(); o.main(); o.flush();
	}

	void main() {
		int l = sc.nextInt();
		double a = l / 3.0;
		printf("%.6f\n", a * a * a);
	}
}
