<image>As shown in the figure, a ship is located at point $$A$$, which is $$4$$ nautical miles away from the lighthouse $$P$$ in the direction of $$30^\circ$$ North of East. The ship sails _________ nautical miles in the direction of $$30^\circ$$ South of East to reach point $$B$$, which is due East of the lighthouse $$P$$. 