You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R,4S,4aS,8aS)-4-ethyl-1,2-dimethyl-2,3,4a,5,6,7,8,8a-octahydroquinolin-4-ol The above is the IUPAC name of a molecule. Write its molecular formula.
user
C13H25NO
assistant