using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		string text = "One word, duel. Limes said bye.";
    	string pattern = @"\b(?<w>\p{L}+)(?:\P{L}+(?<w>(\p{L})(?<=\1\P{L}+\1)\p{L}*))+\b";
    	Match result = Regex.Match(text, pattern, RegexOptions.IgnoreCase);
    	List<string> output = new List<string>();
    	if (result.Success) 
    	{
    		foreach (Capture c in result.Groups["w"].Captures)
    			output.Add(c.Value);
    	}
        Console.WriteLine(string.Join(", ", output));
	}
}