You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(4R,4aR,9aR)-1-acetyl-4-phenyl-3,4,4a,6,7,8,9,9a-octahydro-2H-pyrido[3,2-b]azepin-5-yl]-3-methoxypropan-1-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H30N2O3
assistant