In a kingdom the King decided that the time has come to find a husband for his princess daughter. The King wanted to find a worthy lad for his princess, so he promised to give his daughter away to the first young (or old) man who would solve the puzzle that has stumped the best of his court mathematicians for years. The puzzle is very simple: In a palace, there are 25 rooms arranged in a square . 5 rows of rooms with 5 rooms in each row. In every room there is a light switch which not only switches on/off the light in that room, but also switches the lights in the adjacent rooms--the room to the right, to the left, the room above and the room below. Initially, all of the lights are turned off. The goal is to turn the lights on in every room of the palace ?