You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Can you give the molecular formula of the molecule 2-fluoro-4-(1-oxo-3-sulfanylidene-10,10a-dihydro-5H-imidazo[1,5-b]isoquinolin-2-yl)benzonitrile ?
user
C18H12FN3OS
assistant