
import java.util.*;
 
public class Main {
	public static void main (String[] args) {
		Scanner in = new Scanner(System.in);
		
		double a = in.nextInt();
		double s = (a/3)* (a/3)* (a/3);
		
		
		System.out.print(s);
      
	}
} import java.util.*; util.* java public class Main {
	public static void main (String[] args) {
		Scanner in = new Scanner(System.in);
		
		double a = in.nextInt();
		double s = (a/3)* (a/3)* (a/3);
		
		
		System.out.print(s);
      
	}
} Main public static void main (String[] args) {
		Scanner in = new Scanner(System.in);
		
		double a = in.nextInt();
		double s = (a/3)* (a/3)* (a/3);
		
		
		System.out.print(s);
      
	} main {
		Scanner in = new Scanner(System.in);
		
		double a = in.nextInt();
		double s = (a/3)* (a/3)* (a/3);
		
		
		System.out.print(s);
      
	} Scanner in = new Scanner(System.in); in new Scanner(System.in) double a = in.nextInt(); a in.nextInt() in.nextInt in double s = (a/3)* (a/3)* (a/3); s (a/3)* (a/3)* (a/3) (a/3)* (a/3)* (a/3) (a/3) a 3 (a/3) a 3 (a/3) a 3 System.out.print(s) System.out.print System.out System System.out s String[] args args public class Main {
	public static void main (String[] args) {
		Scanner in = new Scanner(System.in);
		
		double a = in.nextInt();
		double s = (a/3)* (a/3)* (a/3);
		
		
		System.out.print(s);
      
	}
} public class Main {
	public static void main (String[] args) {
		Scanner in = new Scanner(System.in);
		
		double a = in.nextInt();
		double s = (a/3)* (a/3)* (a/3);
		
		
		System.out.print(s);
      
	}
} Main

import java.util.*;
 
public class Main {
	public static void main (String[] args) {
		Scanner in = new Scanner(System.in);
		
		double a = in.nextInt();
		double s = (a/3)* (a/3)* (a/3);
		
		
		System.out.print(s);
      
	}
}