using System;

class Program
{
    static void Main()
    {

        Training timetable1 = new Training("First Training");

        Console.WriteLine(timetable1.IsPractical());

        timetable1.Add(new Practice("Practical lesson 1.", "Demonstrate Inheritance using multiple classes.", "Lecture 1. Inheritance"));

        Console.WriteLine(timetable1.IsPractical());

        timetable1.Add(new Lecture("Lecture 1.", "Inheritance"));

        Console.WriteLine(timetable1.IsPractical());
    }
}

abstract class TrainingManagement
{
    public string Description { get; set; }

    protected TrainingManagement(string description)
    {
     Description = description;
    }

class Training : TrainingManagement
{
    private Lesson[] _timetable;

    public Training(string description):base(description)
    {
        _timetable = new Lesson[0];
    }

    public void Add(Lesson lesson)
    {
        if (lesson != null)
        {
            Array.Resize(ref _timetable, _timetable.Length + 1);

            _timetable[_timetable.Length - 1] = lesson;

        }
    }

    public bool IsPractical()
    {
        if (_timetable == null || _timetable.Length==0) return false;
        else
        {
            foreach(Lesson item in _timetable)
            {
                if (item as Practice == null) return false;
            }
        }
        return true;
    }

}

abstract class Lesson : TrainingManagement
{
    protected Lesson(string description) : base(description) { }

}
class Lecture : Lesson
{
    public string Theme { get; set; }

    public Lecture(string description, string theme): base(description)
    {
        Theme = theme;
    }
}

class Practice : Lesson
{
    public string TaskCondition { get; set; }

    public string SolutionCondition { get; set; }

    public Practice(string description, string task, string solution): base(description)
    {
        TaskCondition = task;

        SolutionCondition = solution;
    }
}