Where is the paper in the astroknights that leads to the secret entrance in the library?

first, you have to jump in the fountain(top water part) and you will get the gold coin. then bring it to the museum and give it to the guy. then go to the seconed floor of it and clik on the books that are staked on top of each other. then, the guy will say that the books can not move from that spot and will give you a piece of paper that has the library pass, then go to the library's bottom floor and click on the gold sign that says mcm or something like that then the floor will open.