You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2,6-difluorophenyl)-[4-[1-(3-fluorophenyl)pyrazol-4-yl]piperidin-1-yl]methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H18F3N3O
assistant