import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
 
        String input_line = sc.nextLine();
        double L=Double.parseDouble(input_line);
        System.out.print(Math.pow(L/3.0, 3.0));
	}
 
} import java.util.Scanner; Scanner java.util public class Main {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
 
        String input_line = sc.nextLine();
        double L=Double.parseDouble(input_line);
        System.out.print(Math.pow(L/3.0, 3.0));
	}
 
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
 
        String input_line = sc.nextLine();
        double L=Double.parseDouble(input_line);
        System.out.print(Math.pow(L/3.0, 3.0));
	} main {
		Scanner sc = new Scanner(System.in);
 
        String input_line = sc.nextLine();
        double L=Double.parseDouble(input_line);
        System.out.print(Math.pow(L/3.0, 3.0));
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String input_line = sc.nextLine(); input_line sc.nextLine() sc.nextLine sc double L=Double.parseDouble(input_line); L Double.parseDouble(input_line) Double.parseDouble Double input_line System.out.print(Math.pow(L/3.0, 3.0)) System.out.print System.out System System.out Math.pow(L/3.0, 3.0) Math.pow Math L/3.0 L 3.0 3.0 String[] args args public class Main {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
 
        String input_line = sc.nextLine();
        double L=Double.parseDouble(input_line);
        System.out.print(Math.pow(L/3.0, 3.0));
	}
 
} public class Main {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
 
        String input_line = sc.nextLine();
        double L=Double.parseDouble(input_line);
        System.out.print(Math.pow(L/3.0, 3.0));
	}
 
} Main
import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
 
        String input_line = sc.nextLine();
        double L=Double.parseDouble(input_line);
        System.out.print(Math.pow(L/3.0, 3.0));
	}
 
}