/kloc-Go to the library once every 0/2 days.
You see, Xiaoming should go to the library on May 6th and 9th, 12, while Xiaohua should go to the library on May 8th and 12, so they met in the library on May 6th and 9th. Don't be confused by the number of times you go. Xiao Ming went to the library three times from May 6th to May 12, while Xiao Hua went to the library twice from May 8th to May 12. )