using System;

using System.Text.RegularExpressions;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var a = Regex.Matches("AxxxxxBAxxxxxxxxxxBAxxxxB", "A([^B]+)B").Cast<Match>().Select(m => m.Groups[1].Value).ToList();

        var b = a.Cast<Match>().Select(m => m.Groups[1].Value).ToList();

        Console.WriteLine(string.Join("\r\n", b));

    }

}