Missing Pretty Girl

Ten of them traveled and came to this isolated island. Strangely, the tour guide disappeared the next day. There was no one on the island except them. They searched the island and found a large palace. This palace is very mysterious and contains many ancient texts. When they entered the palace, the door was shut and could not be opened. Later, Li Lingzhe calculated that there were 999 small doors in this palace. There is an extremely complicated mathematical question on the left side of each small door. The answer to the mathematical question is the password to open the door. These small doors are made of special materials that are stronger than any steel. After entering, the small door is closed. The door through which they return to the earth is among these 999 doors, but they don't know which one it is. They are looking for the door back to Earth. Every door you open is a new world. Two of the ten of them disappeared as they entered the first door. One is Zhao Meng's twin sister Zhao Qian. One is a little ruffian, He Xiaoshuai who wants to jump into the sea. Inside every little door is a new world.