import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		double L = 0;
		Scanner sc = new Scanner(System.in);
		L = sc.nextInt();
		double X = (L / 3) * (L / 3) * (L / 3);
		//String max = BigDecimal.valueOf(X).toPlainString();
		System.out.println(X);
		sc.close();
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		double L = 0;
		Scanner sc = new Scanner(System.in);
		L = sc.nextInt();
		double X = (L / 3) * (L / 3) * (L / 3);
		//String max = BigDecimal.valueOf(X).toPlainString();
		System.out.println(X);
		sc.close();
	}
} Main public static void main(String[] args) {
		double L = 0;
		Scanner sc = new Scanner(System.in);
		L = sc.nextInt();
		double X = (L / 3) * (L / 3) * (L / 3);
		//String max = BigDecimal.valueOf(X).toPlainString();
		System.out.println(X);
		sc.close();
	} main {
		double L = 0;
		Scanner sc = new Scanner(System.in);
		L = sc.nextInt();
		double X = (L / 3) * (L / 3) * (L / 3);
		//String max = BigDecimal.valueOf(X).toPlainString();
		System.out.println(X);
		sc.close();
	} double L = 0; L 0 Scanner sc = new Scanner(System.in); sc new Scanner(System.in) L = sc.nextInt() L sc.nextInt() sc.nextInt sc double X = (L / 3) * (L / 3) * (L / 3); X (L / 3) * (L / 3) * (L / 3) (L / 3) * (L / 3) * (L / 3) (L / 3) L 3 (L / 3) L 3 (L / 3) L 3 System.out.println(X) System.out.println System.out System System.out X sc.close() sc.close sc String[] args args public class Main {

	public static void main(String[] args) {
		double L = 0;
		Scanner sc = new Scanner(System.in);
		L = sc.nextInt();
		double X = (L / 3) * (L / 3) * (L / 3);
		//String max = BigDecimal.valueOf(X).toPlainString();
		System.out.println(X);
		sc.close();
	}
} public class Main {

	public static void main(String[] args) {
		double L = 0;
		Scanner sc = new Scanner(System.in);
		L = sc.nextInt();
		double X = (L / 3) * (L / 3) * (L / 3);
		//String max = BigDecimal.valueOf(X).toPlainString();
		System.out.println(X);
		sc.close();
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		double L = 0;
		Scanner sc = new Scanner(System.in);
		L = sc.nextInt();
		double X = (L / 3) * (L / 3) * (L / 3);
		//String max = BigDecimal.valueOf(X).toPlainString();
		System.out.println(X);
		sc.close();
	}
}