using System;

​

    public class Program

    {

       public static void Main()

       {

          Console.WriteLine("Hello World".ContainsSubstring("Henry"));

          Console.WriteLine("Hello World".ContainsSubstring("Hank"));

          Console.WriteLine("12345".ContainsSubstring("12abc"));

       }

    }

​

    public static class MyExtensions

    {

       public static bool ContainsSubstring(this string str, string compareValue)

       {

          const int charsToCompare = 2;

          var subString = compareValue.Substring(0, Math.Min(charsToCompare, compareValue.Length));

          if (str.Contains(subString))

          {

             return true;

          }

          else if (compareValue.Length > charsToCompare)

          {

             return str.ContainsSubstring(compareValue.Substring(1));

          }

          return false;

       }

    }