The theoretical round emphasizes the mathematical aspects, where you analyze the properties of a task by means of logic and then explain your solution in words (and maybe some pseudo code). The 5 tasks with the exact rules and requirements for your solutions have been compiled into a booklet:
There is also a little howto for writing solutions to theoretical tasks:
The easiest way to submit is just using the following upload pages. Alternative ways to hand-in your solutions (email, mail, fax) are described in the booklet.