You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2S)-2-[4-(4-ethylpiperazin-1-yl)anilino]-N-(2,3,4-trifluorophenyl)propanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H25F3N4O
assistant