using System;

public class Program

{

    public static void Main()

    {

        string temp="";

        string str="hello world";

        str=str.Replace(" ","");

        for(int i=0;i<=str.Length-1;i++)

        {

            if(i%2 !=0)

            {

                temp += str[i];

            }

        }

        char[] arr=temp.ToCharArray();

        Array.Reverse(arr);

        string rev=new String(arr);

        Console.WriteLine(rev);

    }

}