Classic ball scaling game

Lets play a classic ball scaling game : Suppose there are 12 balls in front of you, their size and shape are exactly the same, no difference can be seen. However, there is one ball in this 12 balls, its weight is different from the other 11, but whether it is heavier or lighter? We dont know. Our task is to find out the "problem ball" by using the only equal arm balance at hand. But you only have a maximum of three weighing opportunities, if you need to weigh the fourth time (and above) to find the "problem ball", so it is considered a loss. Okay, so fasten the seat belt, we are ready to start...