import java.util.*;

public class Main{

	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
        double N = sc.nextInt();
        double ans = N/3;
        System.out.println(Math.pow(ans,3));
      
	}

}

 import java.util.*; util.* java public class Main{

	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
        double N = sc.nextInt();
        double ans = N/3;
        System.out.println(Math.pow(ans,3));
      
	}

} Main public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
        double N = sc.nextInt();
        double ans = N/3;
        System.out.println(Math.pow(ans,3));
      
	} main {

		Scanner sc = new Scanner(System.in);
        double N = sc.nextInt();
        double ans = N/3;
        System.out.println(Math.pow(ans,3));
      
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double N = sc.nextInt(); N sc.nextInt() sc.nextInt sc double ans = N/3; ans N/3 N 3 System.out.println(Math.pow(ans,3)) System.out.println System.out System System.out Math.pow(ans,3) Math.pow Math ans 3 String[] args args public class Main{

	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
        double N = sc.nextInt();
        double ans = N/3;
        System.out.println(Math.pow(ans,3));
      
	}

} public class Main{

	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
        double N = sc.nextInt();
        double ans = N/3;
        System.out.println(Math.pow(ans,3));
      
	}

} Main
import java.util.*;

public class Main{

	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
        double N = sc.nextInt();
        double ans = N/3;
        System.out.println(Math.pow(ans,3));
      
	}

}


