import java.util.*;

class Main {
	Scanner sc;
	int L;
	
	private void calc() {
		sc = new Scanner(System.in);
		L = sc.nextInt();
		double l = L / 3d;
		System.out.println(l*l*l);
	}

	public static void main(String[] args) {
		new Main().calc();
	}
} import java.util.*; util.* java class Main {
	Scanner sc;
	int L;
	
	private void calc() {
		sc = new Scanner(System.in);
		L = sc.nextInt();
		double l = L / 3d;
		System.out.println(l*l*l);
	}

	public static void main(String[] args) {
		new Main().calc();
	}
} Main Scanner sc; sc int L; L private void calc() {
		sc = new Scanner(System.in);
		L = sc.nextInt();
		double l = L / 3d;
		System.out.println(l*l*l);
	} calc {
		sc = new Scanner(System.in);
		L = sc.nextInt();
		double l = L / 3d;
		System.out.println(l*l*l);
	} sc = new Scanner(System.in) sc new Scanner(System.in) L = sc.nextInt() L sc.nextInt() sc.nextInt sc double l = L / 3d; l L / 3d L 3d System.out.println(l*l*l) System.out.println System.out System System.out l*l*l l*l*l l l l public static void main(String[] args) {
		new Main().calc();
	} main {
		new Main().calc();
	} new Main().calc() new Main().calc new Main() String[] args args
import java.util.*;

class Main {
	Scanner sc;
	int L;
	
	private void calc() {
		sc = new Scanner(System.in);
		L = sc.nextInt();
		double l = L / 3d;
		System.out.println(l*l*l);
	}

	public static void main(String[] args) {
		new Main().calc();
	}
}
