private Person onCircle(double nx, double ny){
        for (Person p : model.getPersons()){
            Circle c = (Circle) p.getShape();
            if(c.getCenterX()+2*c.getRadius()>nx && c.getCenterX()-2*c.getRadius()<nx
                    &&
               c.getCenterY()+2*c.getRadius()>ny && c.getCenterY()-2*c.getRadius()<ny 
                    ){
                return p;
            }
        }
        return null;
    }