using System;

using System.Text.RegularExpressions;

using System.Text;

public class Program

{

    public static void Main()

    {

        string input = "=?utf-8?B?2KfbjNmGINuM2qkg2YXYqtmGINiz2KfYr9mHINin2LPYqg==?= =?utf-8?B?2KfbjNmGINuM2qkg2YXYqtmGINiz2KfYr9mHINin2LPYqg==?= =?utf-8?B?2YbYr9is?=";

        Regex regex = new Regex(string.Format("{0}(.*?){1}",Regex.Escape("=?utf-8?B?"), Regex.Escape("?=")));

        var matches = regex.Matches(input);

        foreach (Match match in matches)

        {

            Console.WriteLine(Encoding.UTF8.GetString(Convert.FromBase64String(match.Groups[1].Value)));

        }

    }

}