You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[4-(2-methylpyridin-4-yl)piperazin-1-yl]-2-[3-(trifluoromethyl)phenyl]ethanone by IUPAC nomenclature, provide its molecular formula.
user
C19H20F3N3O
assistant