using System.Collections.Generic;
using System.Globalization;
using System.IO;using System.Text.RegularExpressions;
public static void Main()
Console.WriteLine( Regex.IsMatch(text, "^[0-9]+[A-Z]{0,3}[0-9]+$") && text.Length > 4);
Console.WriteLine( Regex.IsMatch(text, "^[0-9]+$"));