National Institute of Informatics, National Center of Sciences, Hitotsubashi 2-1-2, Chiyoda-ku, Tokyo 101-8430, Japan. tuangthong@grad.nii.ac.jp <tuangthong@grad.nii.ac.jp>|National Institute of Informatics, National Center of Sciences, Hitotsubashi 2-1-2, Chiyoda-ku, Tokyo 101-8430, Japan. tuangthong@grad.nii.ac.jp <tuangthong@grad.nii.ac.jp>|National Institute of Informatics, National Center of Sciences, Hitotsubashi 2-1-2, Chiyoda-ku, Tokyo 101-8430, Japan. tuangthong@grad.nii.ac.jp <tuangthong@grad.nii.ac.jp>