import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double L = sc.nextInt();
        
        //max a*b*c
        // a + b + c 
        double a = 100 * L / 3;

        System.out.println(a*a*a/100/100/100);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double L = sc.nextInt();
        
        //max a*b*c
        // a + b + c 
        double a = 100 * L / 3;

        System.out.println(a*a*a/100/100/100);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double L = sc.nextInt();
        
        //max a*b*c
        // a + b + c 
        double a = 100 * L / 3;

        System.out.println(a*a*a/100/100/100);
    } main {
        Scanner sc = new Scanner(System.in);
        double L = sc.nextInt();
        
        //max a*b*c
        // a + b + c 
        double a = 100 * L / 3;

        System.out.println(a*a*a/100/100/100);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double L = sc.nextInt(); L sc.nextInt() sc.nextInt sc double a = 100 * L / 3; a 100 * L / 3 100 * L 100 L 3 System.out.println(a*a*a/100/100/100) System.out.println System.out System System.out a*a*a/100/100/100 100 a*a*a/100/100/100 a*a*a a*a*a a a a 100 100 100 String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double L = sc.nextInt();
        
        //max a*b*c
        // a + b + c 
        double a = 100 * L / 3;

        System.out.println(a*a*a/100/100/100);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double L = sc.nextInt();
        
        //max a*b*c
        // a + b + c 
        double a = 100 * L / 3;

        System.out.println(a*a*a/100/100/100);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double L = sc.nextInt();
        
        //max a*b*c
        // a + b + c 
        double a = 100 * L / 3;

        System.out.println(a*a*a/100/100/100);
    }
}