Write a C# Sharp program to create a new string using the two middle characters of a given string of even length (at least 2)

using System;
namespace exercises
{
   class Program
    {       
        static void Main(string[] args)
        {
            Console.WriteLine(test("Hell"));
            Console.WriteLine(test("JS"));
            Console.ReadLine();
        }        
         public static string test(string s1)
         {
              return s1.Substring(s1.Length / 2 - 1, 2);
         }
  }
}