bills. Behind the other two are year long subscriptions to jelly of the month club.
You are instructed to select at random one of the doors. You select door # 1. Before revealing what is behind your door, the host opens one of the two doors which you did not select (let's say door # 2) revealing one of the subscriptions. You now know that the million dollars lies behind either the door # 1 (which you chose) or door # 3. Before the door you have chosen is opened, you have the choice of switching your selection from door # 1 to door # 3.
The question is, is it to your advantage to switch doors?

For those who understand the solution, don't give it away.