You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-N-(2,4-dichlorophenyl)-2-[(3S)-3-[6-(trifluoromethyl)-[1,2,4]triazolo[4,3-a]pyridin-3-yl]piperidin-1-yl]propanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H20Cl2F3N5O
assistant