In previous years the first problem was quite easy and the third was quite difficult. This year the three problems are more similar in difficulty, though the first problem will be a little easier than the other two.
It is usually better to get one problem fully correct rather than 3 problems partially completed. There will be no marks for programs that do not compile. In fact there will not normally be marks for a program that does not produce the correct output.
If you haven't attended the competition before, then the previous year's rules may provide some insight.