import java.util.ArrayList;
import java.util.Iterator;
import java.util.NoSuchElementException;

public class SetGeneric <T extends Object>{
    private final ArrayList<T> _places;
    public int Count() {return _places.size();}
    private final int _maxCount;
    public SetGeneric(int count)
    {
        _maxCount = count;
        _places = new ArrayList<>();
    }
    public int Insert(T tanker)
    {
        return Insert(tanker, 0);
    }
    public int Insert(T tanker, int position)
    {
        if (position < 0 || position >= _maxCount)
            return -1;
        _places.add(position, tanker);
        return position;
    }

    public T Remove(int position)
    {
        if (position < 0 || position >= Count())
            return null;
        var returning = _places.get(position);
        _places.remove(position);
        return returning;
    }

    public T Get(int position)
    {
        if (position < 0 || position >= Count())
        {
            return null;
        }
        return _places.get(position);
    }

    public Iterable<T> GetTankers(final Integer maxTankers) {
        return new Iterable<T>() {
            @Override
            public Iterator<T> iterator() {
                return new Iterator<T>() {
                    private int currentIndex = 0;
                    private int count = 0;

                    @Override
                    public boolean hasNext() {
                        return currentIndex < _places.size() && (maxTankers == null || count < maxTankers);
                    }

                    @Override
                    public T next() {
                        if (hasNext()) {
                            count++;
                            return _places.get(currentIndex++);
                        }
                        throw new NoSuchElementException();
                    }

                    @Override
                    public void remove() {
                        throw new UnsupportedOperationException();
                    }
                };
            }
        };
    }
}