import java.util.*;
 
public class Main {
    public static void main(String args[]){
        Scanner stdIn = new Scanner(System.in);
 
        double l = stdIn.nextInt();

        
        

        //int c = stdIn.nextInt();
        //int x = stdIn.nextInt();
        
        
        
        
        // for(int i = 0; i < s.length(); i++){
        //     a[i] = c[i] - 48;
        //     System.out.println(a[i]);
        // }
        //int sum = 0;
        //boolean flag = true;
        //for(int i = 0; i < s.length(); i++){
        //}
 
        System.out.println(String.format("%f", Math.pow(l / 3, 3)));
 
        //System.out.println();
        //System.out.print();
 
        stdIn.close();
    }
} import java.util.*; util.* java public class Main {
    public static void main(String args[]){
        Scanner stdIn = new Scanner(System.in);
 
        double l = stdIn.nextInt();

        
        

        //int c = stdIn.nextInt();
        //int x = stdIn.nextInt();
        
        
        
        
        // for(int i = 0; i < s.length(); i++){
        //     a[i] = c[i] - 48;
        //     System.out.println(a[i]);
        // }
        //int sum = 0;
        //boolean flag = true;
        //for(int i = 0; i < s.length(); i++){
        //}
 
        System.out.println(String.format("%f", Math.pow(l / 3, 3)));
 
        //System.out.println();
        //System.out.print();
 
        stdIn.close();
    }
} Main public static void main(String args[]){
        Scanner stdIn = new Scanner(System.in);
 
        double l = stdIn.nextInt();

        
        

        //int c = stdIn.nextInt();
        //int x = stdIn.nextInt();
        
        
        
        
        // for(int i = 0; i < s.length(); i++){
        //     a[i] = c[i] - 48;
        //     System.out.println(a[i]);
        // }
        //int sum = 0;
        //boolean flag = true;
        //for(int i = 0; i < s.length(); i++){
        //}
 
        System.out.println(String.format("%f", Math.pow(l / 3, 3)));
 
        //System.out.println();
        //System.out.print();
 
        stdIn.close();
    } main {
        Scanner stdIn = new Scanner(System.in);
 
        double l = stdIn.nextInt();

        
        

        //int c = stdIn.nextInt();
        //int x = stdIn.nextInt();
        
        
        
        
        // for(int i = 0; i < s.length(); i++){
        //     a[i] = c[i] - 48;
        //     System.out.println(a[i]);
        // }
        //int sum = 0;
        //boolean flag = true;
        //for(int i = 0; i < s.length(); i++){
        //}
 
        System.out.println(String.format("%f", Math.pow(l / 3, 3)));
 
        //System.out.println();
        //System.out.print();
 
        stdIn.close();
    } Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) double l = stdIn.nextInt(); l stdIn.nextInt() stdIn.nextInt stdIn System.out.println(String.format("%f", Math.pow(l / 3, 3))) System.out.println System.out System System.out String.format("%f", Math.pow(l / 3, 3)) String.format String "%f" Math.pow(l / 3, 3) Math.pow Math l / 3 l 3 3 stdIn.close() stdIn.close stdIn String args[] args public class Main {
    public static void main(String args[]){
        Scanner stdIn = new Scanner(System.in);
 
        double l = stdIn.nextInt();

        
        

        //int c = stdIn.nextInt();
        //int x = stdIn.nextInt();
        
        
        
        
        // for(int i = 0; i < s.length(); i++){
        //     a[i] = c[i] - 48;
        //     System.out.println(a[i]);
        // }
        //int sum = 0;
        //boolean flag = true;
        //for(int i = 0; i < s.length(); i++){
        //}
 
        System.out.println(String.format("%f", Math.pow(l / 3, 3)));
 
        //System.out.println();
        //System.out.print();
 
        stdIn.close();
    }
} public class Main {
    public static void main(String args[]){
        Scanner stdIn = new Scanner(System.in);
 
        double l = stdIn.nextInt();

        
        

        //int c = stdIn.nextInt();
        //int x = stdIn.nextInt();
        
        
        
        
        // for(int i = 0; i < s.length(); i++){
        //     a[i] = c[i] - 48;
        //     System.out.println(a[i]);
        // }
        //int sum = 0;
        //boolean flag = true;
        //for(int i = 0; i < s.length(); i++){
        //}
 
        System.out.println(String.format("%f", Math.pow(l / 3, 3)));
 
        //System.out.println();
        //System.out.print();
 
        stdIn.close();
    }
} Main
import java.util.*;
 
public class Main {
    public static void main(String args[]){
        Scanner stdIn = new Scanner(System.in);
 
        double l = stdIn.nextInt();

        
        

        //int c = stdIn.nextInt();
        //int x = stdIn.nextInt();
        
        
        
        
        // for(int i = 0; i < s.length(); i++){
        //     a[i] = c[i] - 48;
        //     System.out.println(a[i]);
        // }
        //int sum = 0;
        //boolean flag = true;
        //for(int i = 0; i < s.length(); i++){
        //}
 
        System.out.println(String.format("%f", Math.pow(l / 3, 3)));
 
        //System.out.println();
        //System.out.print();
 
        stdIn.close();
    }
}