You are a prisoner in the king's dungeon. You just learned that the food you ate was poisoned. The king has given you a chance to escape death and to be released from prison. You have been given a balance (which you can use no more than three times) and 12 pills with no perceptible differences. You know the following about the pills:
1. One pill is the antidote to the poison, the other 11 will not help you.
2. The antidote pill does not weigh the same as the other pills, but you do not know if it weighs more or less than the other pills.
3. You do not know if the other 11 pills have poison in them.
Using the balance no more than three times, tell me how you would determine which pill is the antidote.