1. Institute of Applied Mathematics and Mechanics, Faculty of Mathematics, Informatics and Mechanics, University of Warsaw, ul. Banacha 2, 02-097 Warsaw, Poland
2. Institute of Mathematics, University of Gdańsk, ul. Wita Stwosza 57, 80-308 Gdańsk, Poland
3. ANGE Project-Team (INRIA, CEREMA, UPMC, CNRS), LJLL, UPMC Université Paris VI, Sorbonne Universités, UMR CNRS 7958, 2 rue Simone Iff — CS 42112 — 75589 Paris Cedex 12, France