import java.util.*;

class Main {
  public static void main (String[] args) throws java.lang.Exception {
    Scanner scanner = new Scanner(System.in);
    int L = scanner.nextInt();
    double result = ATCoder_abc159_c.largestVolume(L);
    System.out.printf("%f\n", result);
  }
}

class ATCoder_abc159_c {
    // Per Euclidean math, largest possible volume is a cube.
	public static double largestVolume(int L) {
		double lOver3 = (double) L / 3.0;
		double volume = lOver3 * lOver3 * lOver3;
      	return volume;
	}
} import java.util.*; util.* java class Main {
  public static void main (String[] args) throws java.lang.Exception {
    Scanner scanner = new Scanner(System.in);
    int L = scanner.nextInt();
    double result = ATCoder_abc159_c.largestVolume(L);
    System.out.printf("%f\n", result);
  }
} Main public static void main (String[] args) throws java.lang.Exception {
    Scanner scanner = new Scanner(System.in);
    int L = scanner.nextInt();
    double result = ATCoder_abc159_c.largestVolume(L);
    System.out.printf("%f\n", result);
  } main {
    Scanner scanner = new Scanner(System.in);
    int L = scanner.nextInt();
    double result = ATCoder_abc159_c.largestVolume(L);
    System.out.printf("%f\n", result);
  } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) int L = scanner.nextInt(); L scanner.nextInt() scanner.nextInt scanner double result = ATCoder_abc159_c.largestVolume(L); result ATCoder_abc159_c.largestVolume(L) ATCoder_abc159_c.largestVolume ATCoder_abc159_c L System.out.printf("%f\n", result) System.out.printf System.out System System.out "%f\n" result String[] args args class ATCoder_abc159_c {
    // Per Euclidean math, largest possible volume is a cube.
	public static double largestVolume(int L) {
		double lOver3 = (double) L / 3.0;
		double volume = lOver3 * lOver3 * lOver3;
      	return volume;
	}
} ATCoder_abc159_c // Per Euclidean math, largest possible volume is a cube.
	public static double largestVolume(int L) {
		double lOver3 = (double) L / 3.0;
		double volume = lOver3 * lOver3 * lOver3;
      	return volume;
	} largestVolume {
		double lOver3 = (double) L / 3.0;
		double volume = lOver3 * lOver3 * lOver3;
      	return volume;
	} double lOver3 = (double) L / 3.0; lOver3 (double) L / 3.0 (double) L 3.0 double volume = lOver3 * lOver3 * lOver3; volume lOver3 * lOver3 * lOver3 lOver3 * lOver3 * lOver3 lOver3 lOver3 lOver3 return volume; volume int L L
import java.util.*;

class Main {
  public static void main (String[] args) throws java.lang.Exception {
    Scanner scanner = new Scanner(System.in);
    int L = scanner.nextInt();
    double result = ATCoder_abc159_c.largestVolume(L);
    System.out.printf("%f\n", result);
  }
}

class ATCoder_abc159_c {
    // Per Euclidean math, largest possible volume is a cube.
	public static double largestVolume(int L) {
		double lOver3 = (double) L / 3.0;
		double volume = lOver3 * lOver3 * lOver3;
      	return volume;
	}
}
