import java.math.BigDecimal;
import java.util.Scanner;

 
public class Main {
 
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		
		double temp = Math.pow(L, 3) / 27;
		System.out.println(BigDecimal.valueOf(temp));
		sc.close();
		
	}
	
} import java.math.BigDecimal; BigDecimal java.math import java.util.Scanner; Scanner java.util public class Main {
 
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		
		double temp = Math.pow(L, 3) / 27;
		System.out.println(BigDecimal.valueOf(temp));
		sc.close();
		
	}
	
} Main public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		
		double temp = Math.pow(L, 3) / 27;
		System.out.println(BigDecimal.valueOf(temp));
		sc.close();
		
	} main {
		
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		
		double temp = Math.pow(L, 3) / 27;
		System.out.println(BigDecimal.valueOf(temp));
		sc.close();
		
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int L = sc.nextInt(); L sc.nextInt() sc.nextInt sc double temp = Math.pow(L, 3) / 27; temp Math.pow(L, 3) / 27 Math.pow(L, 3) Math.pow Math L 3 27 System.out.println(BigDecimal.valueOf(temp)) System.out.println System.out System System.out BigDecimal.valueOf(temp) BigDecimal.valueOf BigDecimal temp sc.close() sc.close sc String[] args args public class Main {
 
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		
		double temp = Math.pow(L, 3) / 27;
		System.out.println(BigDecimal.valueOf(temp));
		sc.close();
		
	}
	
} public class Main {
 
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		
		double temp = Math.pow(L, 3) / 27;
		System.out.println(BigDecimal.valueOf(temp));
		sc.close();
		
	}
	
} Main
import java.math.BigDecimal;
import java.util.Scanner;

 
public class Main {
 
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		int L = sc.nextInt();
		
		double temp = Math.pow(L, 3) / 27;
		System.out.println(BigDecimal.valueOf(temp));
		sc.close();
		
	}
	
}