But the one upstairs is wrong.

Take two tablets first.

After that, we'll see how B takes it. If b takes 1, then a takes 3, if b takes 2, then a takes 2, if b takes 3, then a takes 1. In short, the sum of the matches taken by two people in each round is four, so in the end, after taking all the matches in 2002, A took three more, and then A took all of them.

Because there are only four matchsticks in each round, you can do it every time. If you take five matches at a time, then B must take at least two. But if B takes 1, then A won't win in the end. If you take three matches at a time, take at most two. If B gets three, A won't win in the end! You got it?