import java.math.BigDecimal;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		double L = scan.nextDouble();


		BigDecimal Max = new BigDecimal(Math.pow(L/3, 3));

		System.out.printf(Max.toPlainString());
		scan.close();

	}

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

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		double L = scan.nextDouble();


		BigDecimal Max = new BigDecimal(Math.pow(L/3, 3));

		System.out.printf(Max.toPlainString());
		scan.close();

	}

} Main public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		double L = scan.nextDouble();


		BigDecimal Max = new BigDecimal(Math.pow(L/3, 3));

		System.out.printf(Max.toPlainString());
		scan.close();

	} main {

		Scanner scan = new Scanner(System.in);

		double L = scan.nextDouble();


		BigDecimal Max = new BigDecimal(Math.pow(L/3, 3));

		System.out.printf(Max.toPlainString());
		scan.close();

	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) double L = scan.nextDouble(); L scan.nextDouble() scan.nextDouble scan BigDecimal Max = new BigDecimal(Math.pow(L/3, 3)); Max new BigDecimal(Math.pow(L/3, 3)) System.out.printf(Max.toPlainString()) System.out.printf System.out System System.out Max.toPlainString() Max.toPlainString Max scan.close() scan.close scan String[] args args public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		double L = scan.nextDouble();


		BigDecimal Max = new BigDecimal(Math.pow(L/3, 3));

		System.out.printf(Max.toPlainString());
		scan.close();

	}

} public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		double L = scan.nextDouble();


		BigDecimal Max = new BigDecimal(Math.pow(L/3, 3));

		System.out.printf(Max.toPlainString());
		scan.close();

	}

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

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		double L = scan.nextDouble();


		BigDecimal Max = new BigDecimal(Math.pow(L/3, 3));

		System.out.printf(Max.toPlainString());
		scan.close();

	}

}
