You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(10aS)-2-prop-2-enyl-3-sulfanylidene-10,10a-dihydro-5H-imidazo[1,5-b]isoquinolin-1-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C14H14N2OS
assistant