1. Faculty of Mathematics and Computer Science, University of Łódź, Poland. {doliwa,horzel,jarocki}@math.uni.lodz.pl
2. Institute of Computer Science, University of Natural Sciences and Humanities, Poland. artur@iis.ap.siedlce.pl
3. Institute of Computer Science PAS and University of Natural Sciences and Humanities, Poland. penczek@ipipan.waw.pl
4. Faculty of Mathematics and Computer Science, University of Łódź, Poland. polrola@math.uni.lodz.pl
5. Institute of Computer Science PAS, Poland. mszreter@ipipan.waw.pl
6. Institute of Mathematics and Computer Science, Jan Długosz University in Częstochowa, Poland. a.zbrzezny@ajd.czest.pl