You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl-[(2-methylphenyl)methyl]-[(2R)-1-oxo-1-(2,3,4-trifluoroanilino)propan-2-yl]azanium is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H20F3N2O+
assistant