using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string str1 = "<tag tsdfg> some other random text";

        string str2 = "<tag sdfgsdfgfsdg> some other random text";

        string str3 = "<tag 1564> some other random text";

        str1 = Regex.Replace(str1, @"\<tag.*\>", "<tag>");

        Console.WriteLine(str1);

        str2 = Regex.Replace(str2, @"\<tag.*\>", "<tag>");

        Console.WriteLine(str1);

    }

}