using System;
using System.Text.RegularExpressions;
 
public class Test
{
public static void Main()
{
string str = "Only 'together' can we turn him to the 'dark side' of the Force";
string result = Regex.Replace(str, @"('[^']*\bdark\b[^']*')|'[^']*'", "$1");
Console.WriteLine(result);
Console.ReadLine();
}
}