According to the regulations for admission of new students at Sofia University, all students successfully finished 12th grade with a valid diploma, and having achieved excellent result of the Bulgarian National Networking Competition, don't need to take exams in order to enter the Faculty of Mathematics and Informatics. Their excellent marks from the competition are recognized as results from the admission exams. All candidates with such excellent marks need to take their official letter with marks from the Dean of the faculty and use it during the admission. This could be done in the beginning of May.
For more information (in Bulgarian) look at the web site of the networking competition.