using System;

using System.Text;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Reverse("Hello World"));

    }

    public static string Reverse(string inp)

    {

        StringBuilder sb = new StringBuilder();

        for(int i=inp.Length - 1; i>=0; i--)

        {

            sb.Append(inp[i]);

        }

        return sb.ToString();

    }

}