import java.util.*;
import java.math.BigDecimal;
 
public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double L = sc.nextDouble();
		//double taiseki = Math.pow(L/3.0,3.0);
		//System.out.println(taiseki);
		BigDecimal ans = new BigDecimal(Math.pow((L/3),3));
		System.out.println(ans.toPlainString());
	}
} import java.util.*; util.* java import java.math.BigDecimal; BigDecimal java.math public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double L = sc.nextDouble();
		//double taiseki = Math.pow(L/3.0,3.0);
		//System.out.println(taiseki);
		BigDecimal ans = new BigDecimal(Math.pow((L/3),3));
		System.out.println(ans.toPlainString());
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double L = sc.nextDouble();
		//double taiseki = Math.pow(L/3.0,3.0);
		//System.out.println(taiseki);
		BigDecimal ans = new BigDecimal(Math.pow((L/3),3));
		System.out.println(ans.toPlainString());
	} main {
		Scanner sc = new Scanner(System.in);
		double L = sc.nextDouble();
		//double taiseki = Math.pow(L/3.0,3.0);
		//System.out.println(taiseki);
		BigDecimal ans = new BigDecimal(Math.pow((L/3),3));
		System.out.println(ans.toPlainString());
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double L = sc.nextDouble(); L sc.nextDouble() sc.nextDouble sc BigDecimal ans = new BigDecimal(Math.pow((L/3),3)); ans new BigDecimal(Math.pow((L/3),3)) System.out.println(ans.toPlainString()) System.out.println System.out System System.out ans.toPlainString() ans.toPlainString ans String[] args args public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double L = sc.nextDouble();
		//double taiseki = Math.pow(L/3.0,3.0);
		//System.out.println(taiseki);
		BigDecimal ans = new BigDecimal(Math.pow((L/3),3));
		System.out.println(ans.toPlainString());
	}
} public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double L = sc.nextDouble();
		//double taiseki = Math.pow(L/3.0,3.0);
		//System.out.println(taiseki);
		BigDecimal ans = new BigDecimal(Math.pow((L/3),3));
		System.out.println(ans.toPlainString());
	}
} Main
import java.util.*;
import java.math.BigDecimal;
 
public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		double L = sc.nextDouble();
		//double taiseki = Math.pow(L/3.0,3.0);
		//System.out.println(taiseki);
		BigDecimal ans = new BigDecimal(Math.pow((L/3),3));
		System.out.println(ans.toPlainString());
	}
}