Turn right into the office, make a right again between the bookshelves and then a quick left. Turn into the second doorway on the left. Stop and wait near the toilet.
Go straight and enter the room. Turn right and go out the door. Turn left and go through the hallway until you get to the second door on the left. Enter the room and wait near the toilet.
With the long corridor behind you, there will be a door to your left and a double door in front of you. Go through the double door in front of you. Exit this room through the opening in the corner of the room that's ahead of you and to the right. After passing the bookcase on your left (which is also a concealed door that you just went through), turn ninety degrees to the left and enter the second toilet area to your left.