Department of Computer Science, National Tsing Hua University, Hsinchu, 300, Taiwan. cllu@cs.nthu.edu.tw.|Department of Computer Science, National Tsing Hua University, Hsinchu, 300, Taiwan. holystu@gmail.com.|Department of Computer Science, National Tsing Hua University, Hsinchu, 300, Taiwan. happyday5296@hotmail.com.|Department of Chemistry, National Cheng Kung University, Tainan City, 701, Taiwan. hchiu@mail.ncku.edu.tw.