import java.util.*;
import java.math.*;
import java.text.*;

public class Main{

    public static void main(String args[]){
       Scanner sc = new Scanner(System.in);
		BigDecimal l = new BigDecimal(sc.nextLine());
		BigDecimal three = new BigDecimal("3");
		//DecimalFormat df = new decimalFormat("0.000000000000"):
		BigDecimal res = l.divide(three, 12, RoundingMode.HALF_UP).pow(3);
		
		System.out.println(res);
    }
	
	public static boolean isKai(String s){
		return s.equals(new StringBuilder(s).reverse().toString());
	}
}

 import java.util.*; util.* java import java.math.*; math.* java import java.text.*; text.* java public class Main{

    public static void main(String args[]){
       Scanner sc = new Scanner(System.in);
		BigDecimal l = new BigDecimal(sc.nextLine());
		BigDecimal three = new BigDecimal("3");
		//DecimalFormat df = new decimalFormat("0.000000000000"):
		BigDecimal res = l.divide(three, 12, RoundingMode.HALF_UP).pow(3);
		
		System.out.println(res);
    }
	
	public static boolean isKai(String s){
		return s.equals(new StringBuilder(s).reverse().toString());
	}
} Main public static void main(String args[]){
       Scanner sc = new Scanner(System.in);
		BigDecimal l = new BigDecimal(sc.nextLine());
		BigDecimal three = new BigDecimal("3");
		//DecimalFormat df = new decimalFormat("0.000000000000"):
		BigDecimal res = l.divide(three, 12, RoundingMode.HALF_UP).pow(3);
		
		System.out.println(res);
    } main {
       Scanner sc = new Scanner(System.in);
		BigDecimal l = new BigDecimal(sc.nextLine());
		BigDecimal three = new BigDecimal("3");
		//DecimalFormat df = new decimalFormat("0.000000000000"):
		BigDecimal res = l.divide(three, 12, RoundingMode.HALF_UP).pow(3);
		
		System.out.println(res);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) BigDecimal l = new BigDecimal(sc.nextLine()); l new BigDecimal(sc.nextLine()) BigDecimal three = new BigDecimal("3"); three new BigDecimal("3") BigDecimal res = l.divide(three, 12, RoundingMode.HALF_UP).pow(3); res l.divide(three, 12, RoundingMode.HALF_UP).pow(3) l.divide(three, 12, RoundingMode.HALF_UP).pow l.divide(three, 12, RoundingMode.HALF_UP) l.divide l three 12 RoundingMode.HALF_UP RoundingMode RoundingMode.HALF_UP 3 System.out.println(res) System.out.println System.out System System.out res String args[] args public static boolean isKai(String s){
		return s.equals(new StringBuilder(s).reverse().toString());
	} isKai {
		return s.equals(new StringBuilder(s).reverse().toString());
	} return s.equals(new StringBuilder(s).reverse().toString()); s.equals(new StringBuilder(s).reverse().toString()) s.equals s new StringBuilder(s).reverse().toString() new StringBuilder(s).reverse().toString new StringBuilder(s).reverse() new StringBuilder(s).reverse new StringBuilder(s) String s s public class Main{

    public static void main(String args[]){
       Scanner sc = new Scanner(System.in);
		BigDecimal l = new BigDecimal(sc.nextLine());
		BigDecimal three = new BigDecimal("3");
		//DecimalFormat df = new decimalFormat("0.000000000000"):
		BigDecimal res = l.divide(three, 12, RoundingMode.HALF_UP).pow(3);
		
		System.out.println(res);
    }
	
	public static boolean isKai(String s){
		return s.equals(new StringBuilder(s).reverse().toString());
	}
} public class Main{

    public static void main(String args[]){
       Scanner sc = new Scanner(System.in);
		BigDecimal l = new BigDecimal(sc.nextLine());
		BigDecimal three = new BigDecimal("3");
		//DecimalFormat df = new decimalFormat("0.000000000000"):
		BigDecimal res = l.divide(three, 12, RoundingMode.HALF_UP).pow(3);
		
		System.out.println(res);
    }
	
	public static boolean isKai(String s){
		return s.equals(new StringBuilder(s).reverse().toString());
	}
} Main
import java.util.*;
import java.math.*;
import java.text.*;

public class Main{

    public static void main(String args[]){
       Scanner sc = new Scanner(System.in);
		BigDecimal l = new BigDecimal(sc.nextLine());
		BigDecimal three = new BigDecimal("3");
		//DecimalFormat df = new decimalFormat("0.000000000000"):
		BigDecimal res = l.divide(three, 12, RoundingMode.HALF_UP).pow(3);
		
		System.out.println(res);
    }
	
	public static boolean isKai(String s){
		return s.equals(new StringBuilder(s).reverse().toString());
	}
}


