FancyBarcodes-ExamPreparation

using System;
using System.Text.RegularExpressions;

namespace FancyBarcodes
{
    class Program
    {
        static void Main(string[] args)
        {
            int numberOfLines = int.Parse(Console.ReadLine());
            Regex regexForBarcode = new Regex(@"@#+[A-Z][A-Za-z0-9]{4,}[A-Z]@#+");
            Regex regexForDigits = new Regex(@"[0-9]");
            for (int i = 0; i < numberOfLines; i++)
            {
                string barcodeInput = Console.ReadLine();
                Match matchValidBarcode = regexForBarcode.Match(barcodeInput);
                MatchCollection matchesDigits = regexForDigits.Matches(barcodeInput);

                if (matchValidBarcode.Success)
                {
                    string productGroup = "00";
                    if (regexForDigits.IsMatch(barcodeInput))
                    {
                        productGroup = string.Empty;
                        foreach (Match matches in matchesDigits)
                        {
                            productGroup += matches.Value;
                        }
                    }

                    Console.WriteLine($"Product group: {productGroup}");
                }

                else
                {
                    Console.WriteLine("Invalid barcode");
                }
            }
        }
    }
}