Figure - (Doors)

You reached door 50 after passing a long path of so many doors. You open it when you enter and you see that it is like a library. Upon entering, the door makes a loud noise that caught the attention of something in the room. I heard the door open and I look around the place looking for who made the noise "It seems like someone has arrived" He starts to approach the door but another noise distracts me giving him the opportunity to enter