Each competition has a single paper of 5 questions to answer in 4 hours. So there are a total of 90 problems to date. I have put up solutions for all the problems except 04/3, 04/4 and 04/5.

Like the IMO, the difficulty of the questions is variable. Some are easy, some are hard. The general pattern is for the questions to be arranged in order of increasing difficulty. The questions got harder around 1997, but now seem to be getting easier again.