import java.util.*;
public class Main {
	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
		double L = sc.nextInt();

        double ans= (L/3)*(L/3)*(L/3);
        System.out.println(String.format("%.8f",ans));
        }
    } import java.util.*; util.* java public class Main {
	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
		double L = sc.nextInt();

        double ans= (L/3)*(L/3)*(L/3);
        System.out.println(String.format("%.8f",ans));
        }
    } Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
		double L = sc.nextInt();

        double ans= (L/3)*(L/3)*(L/3);
        System.out.println(String.format("%.8f",ans));
        } main {
        Scanner sc = new Scanner(System.in);
		double L = sc.nextInt();

        double ans= (L/3)*(L/3)*(L/3);
        System.out.println(String.format("%.8f",ans));
        } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double L = sc.nextInt(); L sc.nextInt() sc.nextInt sc double ans= (L/3)*(L/3)*(L/3); ans (L/3)*(L/3)*(L/3) (L/3)*(L/3)*(L/3) (L/3) L 3 (L/3) L 3 (L/3) L 3 System.out.println(String.format("%.8f",ans)) System.out.println System.out System System.out String.format("%.8f",ans) String.format String "%.8f" ans String[] args args public class Main {
	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
		double L = sc.nextInt();

        double ans= (L/3)*(L/3)*(L/3);
        System.out.println(String.format("%.8f",ans));
        }
    } public class Main {
	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
		double L = sc.nextInt();

        double ans= (L/3)*(L/3)*(L/3);
        System.out.println(String.format("%.8f",ans));
        }
    } Main
import java.util.*;
public class Main {
	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
		double L = sc.nextInt();

        double ans= (L/3)*(L/3)*(L/3);
        System.out.println(String.format("%.8f",ans));
        }
    }