import java.util.*;
import java.math.*;
public class Main {
    public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int totalLength = Integer.parseInt(sc.next());
      	double length=(double)totalLength/3;
    	System.out.println(BigDecimal.valueOf(Math.pow(length,3d)).toPlainString());
    }

} import java.util.*; util.* java import java.math.*; math.* java public class Main {
    public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int totalLength = Integer.parseInt(sc.next());
      	double length=(double)totalLength/3;
    	System.out.println(BigDecimal.valueOf(Math.pow(length,3d)).toPlainString());
    }

} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int totalLength = Integer.parseInt(sc.next());
      	double length=(double)totalLength/3;
    	System.out.println(BigDecimal.valueOf(Math.pow(length,3d)).toPlainString());
    } main {
		Scanner sc = new Scanner(System.in);
		int totalLength = Integer.parseInt(sc.next());
      	double length=(double)totalLength/3;
    	System.out.println(BigDecimal.valueOf(Math.pow(length,3d)).toPlainString());
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int totalLength = Integer.parseInt(sc.next()); totalLength Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc double length=(double)totalLength/3; length (double)totalLength/3 (double)totalLength 3 System.out.println(BigDecimal.valueOf(Math.pow(length,3d)).toPlainString()) System.out.println System.out System System.out BigDecimal.valueOf(Math.pow(length,3d)).toPlainString() BigDecimal.valueOf(Math.pow(length,3d)).toPlainString BigDecimal.valueOf(Math.pow(length,3d)) BigDecimal.valueOf BigDecimal Math.pow(length,3d) Math.pow Math length 3d String[] args args public class Main {
    public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int totalLength = Integer.parseInt(sc.next());
      	double length=(double)totalLength/3;
    	System.out.println(BigDecimal.valueOf(Math.pow(length,3d)).toPlainString());
    }

} public class Main {
    public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int totalLength = Integer.parseInt(sc.next());
      	double length=(double)totalLength/3;
    	System.out.println(BigDecimal.valueOf(Math.pow(length,3d)).toPlainString());
    }

} Main
import java.util.*;
import java.math.*;
public class Main {
    public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int totalLength = Integer.parseInt(sc.next());
      	double length=(double)totalLength/3;
    	System.out.println(BigDecimal.valueOf(Math.pow(length,3d)).toPlainString());
    }

}