1. Faculty of Mechanics and Mathematics, Kazakhstan Branch of M.V. Lomonosov Moscow State University, Astana 010010, Kazakhstan
2. Institute of Mathematics and Mathematical Modeling, Almaty 050010, Kazakhstan
3. Department of Differential Equations, Faculty of Mechanics and Mathematics, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia
4. Institute of Mathematics with Computing Center, Subdivision of the Ufa Federal Research Center of Russian Academy of Science, 450008 Ufa, Russia
5. Institute for Information Transmission Problems, Russian Academy of Sciences, 127051 Moscow, Russia