You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 2-(4-chloro-N-(4-methyl-3,4,5,6-tetrahydro-2H-azepin-7-yl)anilino)-1-(4-chlorophenyl)ethanone .
user
C21H22Cl2N2O
assistant