You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [5-(3,4-dichlorophenyl)furan-2-yl]-(3,4-dihydro-1H-isoquinolin-2-yl)methanethione by IUPAC nomenclature, provide its molecular formula.
user
C20H15Cl2NOS
assistant