出单双出现规律的公式百度一下

简介：Seeing Xiao Xiaobai being led straight to the stairs at the end of the corridor by his grandson Yuanyuan, Sun Feifei, who followed behind with her shoes in hand, couldn't help but said hurriedly: Xiao Xiaobai, are you okay? We still have to go downstairs to the infirmary, which is not that close.