Consider a closed-loop control system with unity negative feedback and  in the forward path, where the gain . The complete Nyquist plot of the transfer function  is shown in the figure. Note that the Nyquist contour has been chosen to have the clockwise sense. Assume  has no poles on the closed right-half of the complex plane. The number of poles of the closed-loop transfer function in the closed right-half of the complex plane is ________.