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CSharp · Console

/Program.cs

using System;
using System.Text.RegularExpressions;
					
public class Program
{
	public static void Main()
	{
		var  regex = new Regex(@"(\d{2})");
		
		string aString = "040204220442040004200404020602260246";
		string replaced = regex.Replace(aString, "x$1 ");
		Console.WriteLine(replaced);
	}
}