You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
ethyl (4R)-4-(2,3-dichlorophenyl)-6-methyl-2-(2-methylpropylsulfanyl)-1,4-dihydropyrimidine-5-carboxylate is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H22Cl2N2O2S
assistant