You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
10-bromo-6-(4-methylsulfanylphenyl)-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinoline is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H20BrNS
assistant