1. Institute of Mathematics, The University of Warsaw, Warsaw, Poland. szczuka@mimuw.edu.pl
2. Systems Research Institute, Polish Academy of Sciences and Dituel Sp. z o.o., Warsaw, Poland. l.sosnowski@dituel.pl
3. Section of Computer Science, The Main School of Fire Service, Warsaw, Poland. krasuski@inf.sgsp.edu.pl, krenski@inf.sgsp.edu.pl