You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-2-[4-(4-fluorophenyl)piperazin-1-yl]ethanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C23H28FN3O3
assistant