You have just inherited the family home, empty since your grandfather blew himself to smithereens in a chemistry experiment at the age of 93. There are three switches in the front hall marked simply "attic lights", but from what you have seen of the spaghetti wiring that runs through this building, the circuits from the switches to the lights cannot be easily traced. There are many flights of stairs ascending through generations of style and safety, and you only want to climb up there once. How do you set the switches so that when you do climb to the top floor you will know immediately which switch goes to which lightbulb?