abstract class Clusterable<T> {
    protected long id;
    abstract long getID();
    abstract double getDistance(T element);
}

class Cluster<T extends Clusterable> {
    private Map<Long, T> elements;

    public Cluster(){
        elements = new HashMap<>();
    }

    void addItem(T t){
        elements.put(t.getID(), t);
    }

    void near(long id, int top){
        T element = elements.get(id);
        elements.values()
                .stream()
                .sorted(Comparator.comparingDouble(element::getDistance))
                .skip(1) // se skoka sam sebe, nz dali vaka treba ili ne
                .limit(top)
                .forEach(System.out::println);
    }
}

class Point2D extends Clusterable<Point2D> {
    private float x, y;

    public Point2D(long id, float x, float y){
        this.id = id;
        this.x = x;
        this.y = y;
    }

    @Override
    long getID() {
        return id;
    }

    @Override
    double getDistance(Point2D element) {
        return Math.sqrt((x - element.x) * (x - element.x) + (y - element.y) * (y - element.y));
    }

    @Override
    public String toString(){
        return String.format("%d: (%.0f,%.0f)",id,x,y);
    }
}