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 3-(2-fluoro-4-methylsulfonylanilino)-1-[1-(5-methoxypyrazin-2-yl)piperidin-4-yl]pyrrolidin-2-one ?
user
C21H26FN5O4S
assistant