You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[4-(3-methylsulfonylimidazo[1,5-a]pyridine-1-carbonyl)piperazin-1-yl]-[3-(trifluoromethyl)phenyl]methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H19F3N4O4S
assistant