import java.util.*;
class Main{
	public static void main(String args[]){
    	Scanner sc = new Scanner(System.in);
      	int l = sc.nextInt();
        System.out.println(String.format("%.12f",(double)(l * l * l)/27));
    }
} import java.util.*; util.* java class Main{
	public static void main(String args[]){
    	Scanner sc = new Scanner(System.in);
      	int l = sc.nextInt();
        System.out.println(String.format("%.12f",(double)(l * l * l)/27));
    }
} Main public static void main(String args[]){
    	Scanner sc = new Scanner(System.in);
      	int l = sc.nextInt();
        System.out.println(String.format("%.12f",(double)(l * l * l)/27));
    } main {
    	Scanner sc = new Scanner(System.in);
      	int l = sc.nextInt();
        System.out.println(String.format("%.12f",(double)(l * l * l)/27));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int l = sc.nextInt(); l sc.nextInt() sc.nextInt sc System.out.println(String.format("%.12f",(double)(l * l * l)/27)) System.out.println System.out System System.out String.format("%.12f",(double)(l * l * l)/27) String.format String "%.12f" (double)(l * l * l)/27 (double)(l * l * l) l * l * l l l l 27 String args[] args
import java.util.*;
class Main{
	public static void main(String args[]){
    	Scanner sc = new Scanner(System.in);
      	int l = sc.nextInt();
        System.out.println(String.format("%.12f",(double)(l * l * l)/27));
    }
}