You're stuck in a room that has 2 doors. If you open one you die and if you open the other you live. You don't know which is which. To help you, there are two guys. Both of them know which door to take but one always lies and the other one always says the truth. Of course, you dont know who lies and who says the truth.
How do you get out?
You have to ask either one of them "Which door would the other one say is the right one?"
Then they both point to one door. The liar points to the wrong door because he does the opposite of the truth, and the truth speaking one will point to the wrong door because he will point to the wrong door.
