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