
import java.util.*;

/*

*/



public class Main {
    public static void main(String[] args){

        //スキャン
        Scanner s = new Scanner(System.in);
        float  sumLen =s.nextInt();
        float devi  =sumLen/3;
        float  ans = devi*devi*devi;
        System.out.println(ans);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args){

        //スキャン
        Scanner s = new Scanner(System.in);
        float  sumLen =s.nextInt();
        float devi  =sumLen/3;
        float  ans = devi*devi*devi;
        System.out.println(ans);
    }
} Main public static void main(String[] args){

        //スキャン
        Scanner s = new Scanner(System.in);
        float  sumLen =s.nextInt();
        float devi  =sumLen/3;
        float  ans = devi*devi*devi;
        System.out.println(ans);
    } main {

        //スキャン
        Scanner s = new Scanner(System.in);
        float  sumLen =s.nextInt();
        float devi  =sumLen/3;
        float  ans = devi*devi*devi;
        System.out.println(ans);
    } Scanner s = new Scanner(System.in); s new Scanner(System.in) float  sumLen =s.nextInt(); sumLen s.nextInt() s.nextInt s float devi  =sumLen/3; devi sumLen/3 sumLen 3 float  ans = devi*devi*devi; ans devi*devi*devi devi*devi*devi devi devi devi System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
    public static void main(String[] args){

        //スキャン
        Scanner s = new Scanner(System.in);
        float  sumLen =s.nextInt();
        float devi  =sumLen/3;
        float  ans = devi*devi*devi;
        System.out.println(ans);
    }
} public class Main {
    public static void main(String[] args){

        //スキャン
        Scanner s = new Scanner(System.in);
        float  sumLen =s.nextInt();
        float devi  =sumLen/3;
        float  ans = devi*devi*devi;
        System.out.println(ans);
    }
} Main

import java.util.*;

/*

*/



public class Main {
    public static void main(String[] args){

        //スキャン
        Scanner s = new Scanner(System.in);
        float  sumLen =s.nextInt();
        float devi  =sumLen/3;
        float  ans = devi*devi*devi;
        System.out.println(ans);
    }
}
