import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String W = in.readLine();

		double L = (double) Integer.parseInt(W.split(" ")[0]);

		System.out.println(Math.pow(L/3,3));

	}

} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String W = in.readLine();

		double L = (double) Integer.parseInt(W.split(" ")[0]);

		System.out.println(Math.pow(L/3,3));

	}

} Main public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String W = in.readLine();

		double L = (double) Integer.parseInt(W.split(" ")[0]);

		System.out.println(Math.pow(L/3,3));

	} main {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String W = in.readLine();

		double L = (double) Integer.parseInt(W.split(" ")[0]);

		System.out.println(Math.pow(L/3,3));

	} BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); in new BufferedReader(new InputStreamReader(System.in)) String W = in.readLine(); W in.readLine() in.readLine in double L = (double) Integer.parseInt(W.split(" ")[0]); L (double) Integer.parseInt(W.split(" ")[0]) Integer.parseInt Integer W.split(" ")[0] W.split(" ") W.split W " " 0 System.out.println(Math.pow(L/3,3)) System.out.println System.out System System.out Math.pow(L/3,3) Math.pow Math L/3 L 3 3 String[] args args public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String W = in.readLine();

		double L = (double) Integer.parseInt(W.split(" ")[0]);

		System.out.println(Math.pow(L/3,3));

	}

} public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String W = in.readLine();

		double L = (double) Integer.parseInt(W.split(" ")[0]);

		System.out.println(Math.pow(L/3,3));

	}

} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String W = in.readLine();

		double L = (double) Integer.parseInt(W.split(" ")[0]);

		System.out.println(Math.pow(L/3,3));

	}

}
