import java.util.*;
 
public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		double ans = (L/3.0)*(L/3.0)*(L/3.0);
		System.out.println(String.format("%.7f", ans));
    }
} import java.util.*; util.* java public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		double ans = (L/3.0)*(L/3.0)*(L/3.0);
		System.out.println(String.format("%.7f", ans));
    }
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		double ans = (L/3.0)*(L/3.0)*(L/3.0);
		System.out.println(String.format("%.7f", ans));
    } main {
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		double ans = (L/3.0)*(L/3.0)*(L/3.0);
		System.out.println(String.format("%.7f", ans));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int L = sc.nextInt(); L sc.nextInt() sc.nextInt sc double ans = (L/3.0)*(L/3.0)*(L/3.0); ans (L/3.0)*(L/3.0)*(L/3.0) (L/3.0)*(L/3.0)*(L/3.0) (L/3.0) L 3.0 (L/3.0) L 3.0 (L/3.0) L 3.0 System.out.println(String.format("%.7f", ans)) System.out.println System.out System System.out String.format("%.7f", ans) String.format String "%.7f" ans String[] args args public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		double ans = (L/3.0)*(L/3.0)*(L/3.0);
		System.out.println(String.format("%.7f", ans));
    }
} public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		double ans = (L/3.0)*(L/3.0)*(L/3.0);
		System.out.println(String.format("%.7f", ans));
    }
} Main
import java.util.*;
 
public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		double ans = (L/3.0)*(L/3.0)*(L/3.0);
		System.out.println(String.format("%.7f", ans));
    }
}
