Department of Computer Science, Tokyo Institute of Technology, 2-12-1 Oookayama, Meguro, Tokyo, Japan. atake@bio.cs.titech.ac.jp|Department of Computer Science, Tokyo Institute of Technology, 2-12-1 Oookayama, Meguro, Tokyo, Japan. atake@bio.cs.titech.ac.jp|Department of Computer Science, Tokyo Institute of Technology, 2-12-1 Oookayama, Meguro, Tokyo, Japan. atake@bio.cs.titech.ac.jp|Department of Computer Science, Tokyo Institute of Technology, 2-12-1 Oookayama, Meguro, Tokyo, Japan. atake@bio.cs.titech.ac.jp|Department of Computer Science, Tokyo Institute of Technology, 2-12-1 Oookayama, Meguro, Tokyo, Japan. atake@bio.cs.titech.ac.jp|Department of Computer Science, Tokyo Institute of Technology, 2-12-1 Oookayama, Meguro, Tokyo, Japan. atake@bio.cs.titech.ac.jp