import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long L = sc.nextLong();
		sc.close();
		System.out.println(String.format("%.16f", (double)(L*L*L) / 27));
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long L = sc.nextLong();
		sc.close();
		System.out.println(String.format("%.16f", (double)(L*L*L) / 27));
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long L = sc.nextLong();
		sc.close();
		System.out.println(String.format("%.16f", (double)(L*L*L) / 27));
	} main {
		Scanner sc = new Scanner(System.in);
		long L = sc.nextLong();
		sc.close();
		System.out.println(String.format("%.16f", (double)(L*L*L) / 27));
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long L = sc.nextLong(); L sc.nextLong() sc.nextLong sc sc.close() sc.close sc System.out.println(String.format("%.16f", (double)(L*L*L) / 27)) System.out.println System.out System System.out String.format("%.16f", (double)(L*L*L) / 27) String.format String "%.16f" (double)(L*L*L) / 27 (double)(L*L*L) L*L*L L L L 27 String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long L = sc.nextLong();
		sc.close();
		System.out.println(String.format("%.16f", (double)(L*L*L) / 27));
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long L = sc.nextLong();
		sc.close();
		System.out.println(String.format("%.16f", (double)(L*L*L) / 27));
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long L = sc.nextLong();
		sc.close();
		System.out.println(String.format("%.16f", (double)(L*L*L) / 27));
	}
}