You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[[(1S)-1-(4-chlorophenyl)ethyl]amino]-N-[[4-(difluoromethoxy)phenyl]methyl]-N-methylacetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H21ClF2N2O2
assistant