import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		System.out.printf("%f" , Math.pow((double)L/3, 3) );


	}


}

 import java.util.*; util.* java class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		System.out.printf("%f" , Math.pow((double)L/3, 3) );


	}


} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		System.out.printf("%f" , Math.pow((double)L/3, 3) );


	} main {
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		System.out.printf("%f" , Math.pow((double)L/3, 3) );


	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int L = sc.nextInt(); L sc.nextInt() sc.nextInt sc System.out.printf("%f" , Math.pow((double)L/3, 3) ) System.out.printf System.out System System.out "%f" Math.pow((double)L/3, 3) Math.pow Math (double)L/3 (double)L 3 3 String[] args args
import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		System.out.printf("%f" , Math.pow((double)L/3, 3) );


	}


}


