I have been co-organising and grading at the national high-school Mathematics competition Minko Balkanski
since 2014, after winning it in 2012, which resulted in my going to study at LLG, Paris. For some information on how this happens, see this video and this one, and this leaflet. Since the 2020 edition the competition takes place in the foundation's center in Oryahovitsa. There is a written exam followed by an oral one mimicking competitive exams for French Grandes Ecoles. Look here for more information and here for the problems and solutions of the last twenty or so years. Most importantly, book the dates 12-13 August 2025!
I also contributed to the problem selection and/or grading of the high-school competition PPMG Burgas Challenge
in Mathematics in 2020 and 2022.
I have been part of the committee of the international selection of the ENS since 2024.