1. Department of Computer Science, Chubu University, Kasugai-shi, Aichi, Japan
2. Center for Mathematical Science and Artificial Intelligence, Chubu University, Kasugai-shi, Aichi, Japan
3. Department of Robotics, Chubu University, Kasugai-shi, Aichi, Japan
4. Department of Computer Science, Keio University, Yokohama, Kanagawa, Japan