interface IComponent
{
    void operation();
}
class Leaf : IComponent
{
    public void operation()
    {
        Console.WriteLine("display leaf "+this);
    }
}
class Composite : IComponent
{
    private List<IComponent> _children = new List<IComponent>();

    public void operation()
    {
        Console.WriteLine("display leaf " + this);
    }

    public void AddChild(IComponent component)
    {
        _children.Add(component);
    }

    public void RemoveChild(IComponent component)
    {
        _children.Remove(component);
    }

    public List<IComponent> GetChild()
    {
        return _children;
    }
}