Describe each subtask in pseudocode.
In the pseudocode, you want to be more precise about exactly where the tiles are placed. 
Place a black tile in the northwest corner.
While the floor is not yet filled, repeat the following steps:
 Repeat this step width / 4 – 1 times: 
 Place a tile east of the previously placed tile. If the previously placed tile was white, pick a black one; 
 otherwise, a white one.
 Locate the tile at the beginning of the row that you just placed. If there is space to the south, place a tile of 
the opposite color below it