import java.util.*;

public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 1000000007;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = (int)1e6 + 1;

	void doIt() {
		double L = (double)sc.nextInt();
		L /= 3;
		System.out.println(L * L * L);
	}

	
	
	public static void main(String[] args) {
		new Main().doIt();
	}

} import java.util.*; util.* java public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 1000000007;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = (int)1e6 + 1;

	void doIt() {
		double L = (double)sc.nextInt();
		L /= 3;
		System.out.println(L * L * L);
	}

	
	
	public static void main(String[] args) {
		new Main().doIt();
	}

} Main Scanner sc = new Scanner(System.in); sc new Scanner(System.in) final int MOD = 1000000007; MOD 1000000007 final int MAX = Integer.MAX_VALUE; MAX Integer.MAX_VALUE Integer Integer.MAX_VALUE final long LMAX = Long.MAX_VALUE; LMAX Long.MAX_VALUE Long Long.MAX_VALUE int len = (int)1e6 + 1; len (int)1e6 + 1 (int)1e6 1 void doIt() {
		double L = (double)sc.nextInt();
		L /= 3;
		System.out.println(L * L * L);
	} doIt {
		double L = (double)sc.nextInt();
		L /= 3;
		System.out.println(L * L * L);
	} double L = (double)sc.nextInt(); L (double)sc.nextInt() sc.nextInt sc L /= 3 L 3 System.out.println(L * L * L) System.out.println System.out System System.out L * L * L L * L * L L L L public static void main(String[] args) {
		new Main().doIt();
	} main {
		new Main().doIt();
	} new Main().doIt() new Main().doIt new Main() String[] args args public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 1000000007;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = (int)1e6 + 1;

	void doIt() {
		double L = (double)sc.nextInt();
		L /= 3;
		System.out.println(L * L * L);
	}

	
	
	public static void main(String[] args) {
		new Main().doIt();
	}

} public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 1000000007;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = (int)1e6 + 1;

	void doIt() {
		double L = (double)sc.nextInt();
		L /= 3;
		System.out.println(L * L * L);
	}

	
	
	public static void main(String[] args) {
		new Main().doIt();
	}

} Main
import java.util.*;

public class Main {
	Scanner sc = new Scanner(System.in);
	final int MOD = 1000000007;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
	int len = (int)1e6 + 1;

	void doIt() {
		double L = (double)sc.nextInt();
		L /= 3;
		System.out.println(L * L * L);
	}

	
	
	public static void main(String[] args) {
		new Main().doIt();
	}

}
