1. CNRS, Institut de Recherches Mathématiques de Rennes (UMR 6625 du CNRS), Campus Beaulieu, 35042 Rennes, France
2. Department of Mathematics and AG Laboratory, National Research University Higher School of Economics, Usacheva St., 6, 119048 Moscow, Russia
3. Independent University of Moscow, Bolshoi Vlassievskii per., 11, 119002 Moscow, Russia