The idea is the same as USACO contests. The contest will be between a period of days (Example 3), and when you "agree to participate" you have N amount of hours to solve the M problems (The problems can be ACM-like as well, that's not a problem).
Apart from that, the admins could evaluate the new problems that are submitted (If the problems are new, because if not some will have advantage), and can make a competition like this when they reach K problems (It is a competition to "introduce" the new problems).
What do you think?
Apart from that, the admins could evaluate the new problems that are submitted (If the problems are new, because if not some will have advantage), and can make a competition like this when they reach K problems (It is a competition to "introduce" the new problems).
What do you think?