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 methyl 4-[2-chloro-4-fluoro-5-(1-methylidene-3-oxo-4,5,6,7-tetrahydroisoindol-2-yl)phenyl]-2-methyl-4-sulfanylidenebutanoate ?
user
C21H21ClFNO3S
assistant