static void Main(string[] args)
{
Console.Write("Enter 0 for open exist file or other for create new: ");
var isNew = Console.ReadLine() != "0";
string fileName = ReadFileName(args, isNew);
var doc = AbstractHandler.CreateInstance(fileName);
var type = doc switch
{
XMLHandler => "xml",
DOCHandler => "doc",
_ => "txt",
};
doc.Open();
doc.Save();
Console.WriteLine($"Type of file'{fileName}' is {type}");
_ = Console.ReadKey();
}