1. Department of Mathematics, Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
2. Department of Byophysics, Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
3. Sobolev Insitute of Mathematics, Novosibirsk 630090, Russia
4. Institute of Computational Mathematics and Mathematical Geophysics SB RAS, Novosibirsk 630090, Russia