using System;

    public class UserEntry

    {

        private readonly string _originalValue;

        public UserEntry(string input)

        {

            _originalValue = input;

        }

        public bool IsInt

        {

            get

            {

                return int.TryParse(_originalValue, out var dummy);

            }           

        }

        public int ToInt()

        {

            return ToInt(default(int));

        }

        public int ToInt(int defaultValue)

        {

            int result;

            bool ok = int.TryParse(_originalValue, out result);

            return ok ? result : defaultValue;

        }

        public override string ToString()

        {

            return _originalValue;

        }

        static public implicit operator UserEntry(string input)

        {

            return new UserEntry(input);

        }

        static public implicit operator Int32(UserEntry input)

        {

            return input.ToInt();

        }

    }

    public class Program

    {

        private const int MaximumOrder = 10;

        public static void Main()

        {

            var n = AskForNumberOfShirts();

            Console.WriteLine("OK, I'll order {0} shirts.", n);

        }

        public static int AskForNumberOfShirts()

        {

            while (true)

            {

                Console.WriteLine("Enter the number of shirts to order:");

                UserEntry entry = Console.ReadLine();

                if (!entry.IsInt)

                {

                    Console.WriteLine("You entered an invalid number.");

                    continue;

                }

                if (entry > MaximumOrder)

                {

                    Console.WriteLine("{0} is too many! Please enter {1} or fewer.", entry, MaximumOrder);

                    continue;

                }

                return entry;

            }

        }

    }