
import java.util.*;

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

import java.util.*;

public class Main {
	static public void main(String args[]){
		Scanner sc=new Scanner(System.in);
		 
		 int l=sc.nextInt();
		 System.out.println((double)(l*l*l)/27);
	}
}