A good deal of tasks from previous editions is available at main.edu.pl. To get a flavour of what the tasks might be like, check the tasks from final rounds of several most recent editions of the contest.
What are the other rounds? Well, this contest takes place annually in Poland and starts with online elimination rounds, each of which lasts from one to three days. There are two divisions. Division B contains easy/medium/hard problems, whereas division A - medium/hard/killer tasks. The first rounds are rather easy. If you prefer something really challenging, try tasks from the fifth round (which lasts for three days). The top 20 contestants from the overall ranklist advance to an onsite final, which, this year, takes place on November 26th in Warsaw, Poland. You can join us and participate online!