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

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    double l = sc.nextDouble();
    BigDecimal  l2 = new BigDecimal(l/3);
    
    System.out.println(l2.multiply(l2).multiply(l2));
    
   
  }
} import java.util.*; util.* java import java.math.*; math.* java class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    double l = sc.nextDouble();
    BigDecimal  l2 = new BigDecimal(l/3);
    
    System.out.println(l2.multiply(l2).multiply(l2));
    
   
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    double l = sc.nextDouble();
    BigDecimal  l2 = new BigDecimal(l/3);
    
    System.out.println(l2.multiply(l2).multiply(l2));
    
   
  } main {
    Scanner sc = new Scanner(System.in);
    double l = sc.nextDouble();
    BigDecimal  l2 = new BigDecimal(l/3);
    
    System.out.println(l2.multiply(l2).multiply(l2));
    
   
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double l = sc.nextDouble(); l sc.nextDouble() sc.nextDouble sc BigDecimal  l2 = new BigDecimal(l/3); l2 new BigDecimal(l/3) System.out.println(l2.multiply(l2).multiply(l2)) System.out.println System.out System System.out l2.multiply(l2).multiply(l2) l2.multiply(l2).multiply l2.multiply(l2) l2.multiply l2 l2 l2 String[] args args
import java.util.*;
import java.math.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    double l = sc.nextDouble();
    BigDecimal  l2 = new BigDecimal(l/3);
    
    System.out.println(l2.multiply(l2).multiply(l2));
    
   
  }
}