using System;
using System.Collections.Generic;
using System.Globalization;
using System.Text;
using System.Text.RegularExpressions;
using System.Reflection;
public class MainClass{
public static void Main(){
Regex r3 = new Regex("((?:abc)|(?:xyz))*");
Console.WriteLine(r3.IsMatch("abcabcxyzabc"));
}
}
True