1. Department of Mathematical Informatics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
2. Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
3. Research Organization of Information and Systems (ROIS), 4-3-13 Toranomon, Minato-ku, Tokyo 105-0001, Japan