using System;
using System.Globalization;

internal static class Program
{
    private static void Main(string[] args)
    {
        if (args.Length != 1)
        {
            Console.Error.WriteLine("Usage: lesson COUNT"); Environment.ExitCode = 2; return;
        }
        if (!int.TryParse(args[0], NumberStyles.None, CultureInfo.InvariantCulture, out int count) || count is < 1 or > 20)
        {
            Console.Error.WriteLine("COUNT must be 1..20"); Environment.ExitCode = 2; return;
        }
        Console.WriteLine($"Requested: {count}");
    }
}