Infosys Developer interview questions

You have a set of 3 light switches outside a closed door. One of them controls the light inside the room. With the door closed from outside the room, you can turn the light switches on or off as many times as you would like. You can go into the room - one time only - to see the light. You cannot see the whether the light is on or off from outside the room, nor can you change the light switches while inside the room. No one else is in the room to help you. The room has no windows. Based on the information above, how would you determine which of the three light switches controls the light inside the room?