You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[1-(3-chlorophenyl)cyclopropyl]-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H22ClNO3
assistant