You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance [(5aS,8S,8aR)-8-ethenyl-8a-hydroxy-1,3,5a,6,7,8-hexahydrocyclopenta[c]azepin-2-yl]-phenylmethanone .
user
C18H21NO2
assistant