A couple of proposals:
You may divide all rating changes by 2 (do it "half-rated") due to specificity of edicational rounds.
Add small score bonuses for successful hacks (hacking is useful for community, so it should be rewarded)

Still can't register in div.2 ((

Registration button didn't work for me...

I solved div.2 D quite fast, but it didn't pass presets. After thinking about possible bugs about 50 mins and stress-testing the solution I decided to change the language implementation from MS C++ to GNU C++ and it passed presets. So the question: is it honest to set such a high precision requirements that submission verdict heavily depends on C++ compiler choice?