chinavisaover65xx

Ning Cheng did not rush to open the tower door on the 72nd floor. He stood beside the tower door with some doubts. It stands to reason that the 71st floor is only slightly more difficult than the 70th floor. Since Xiaoyu can pass the 70th floor, why can't he pass the 71st floor? Ning Cheng thought about this problem for a long time without thinking clearly, so he simply opened the tower door on the 72nd floor....