You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[(4-benzyl-5-methyl-1H-imidazol-2-yl)sulfanylmethyl]-7-bromochromen-2-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H17BrN2O2S
assistant