using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string url1=@"http://someother.com/segment1/segment2/segment3/segment4/segment5/segment6/segment7/segment8/segment9/segment10/segment11/segment12/filename.ext";

        string url2=@"/domain.com/segment1/segment2/segment3/segment4/segment5/segment6/segment7/filename.ext";

        string segment6url=Regex.Replace(url1,"segment[0-57-9]./*","");

        string segment6domainurl=Regex.Replace(url2,"segment[0-57-9]./*","");

        Console.WriteLine(segment6url);

        Console.WriteLine(segment6domainurl);

    }

}