You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(3-fluorophenyl)-N-[2-[6-methyl-4-oxo-2-(trifluoromethyl)quinolin-1-yl]ethyl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H18F4N2O2
assistant