You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-N-(4-chlorophenyl)-2-[4-[2-(3-fluoroanilino)-2-oxoethyl]piperazin-1-yl]propanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H24ClFN4O2
assistant