import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		double L = sc.nextDouble();
		double areaLength = L / 3;

		String printStr = String.format("%.12f", areaLength * areaLength * areaLength);
		System.out.println(printStr);
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		double L = sc.nextDouble();
		double areaLength = L / 3;

		String printStr = String.format("%.12f", areaLength * areaLength * areaLength);
		System.out.println(printStr);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		double L = sc.nextDouble();
		double areaLength = L / 3;

		String printStr = String.format("%.12f", areaLength * areaLength * areaLength);
		System.out.println(printStr);
	} main {
		Scanner sc = new Scanner(System.in);

		double L = sc.nextDouble();
		double areaLength = L / 3;

		String printStr = String.format("%.12f", areaLength * areaLength * areaLength);
		System.out.println(printStr);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double L = sc.nextDouble(); L sc.nextDouble() sc.nextDouble sc double areaLength = L / 3; areaLength L / 3 L 3 String printStr = String.format("%.12f", areaLength * areaLength * areaLength); printStr String.format("%.12f", areaLength * areaLength * areaLength) String.format String "%.12f" areaLength * areaLength * areaLength areaLength * areaLength * areaLength areaLength areaLength areaLength System.out.println(printStr) System.out.println System.out System System.out printStr String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		double L = sc.nextDouble();
		double areaLength = L / 3;

		String printStr = String.format("%.12f", areaLength * areaLength * areaLength);
		System.out.println(printStr);
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		double L = sc.nextDouble();
		double areaLength = L / 3;

		String printStr = String.format("%.12f", areaLength * areaLength * areaLength);
		System.out.println(printStr);
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		double L = sc.nextDouble();
		double areaLength = L / 3;

		String printStr = String.format("%.12f", areaLength * areaLength * areaLength);
		System.out.println(printStr);
	}
}
