You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (4R)-2-amino-4-(4-bromophenyl)-7,7-dimethyl-5-oxo-6,8-dihydro-4H-chromene-3-carbothioamide into molecular formula.
user
C18H19BrN2O2S
assistant