You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (3R,7aR)-6-(4-bromophenyl)-3-(4-ethoxy-3-methoxyphenyl)-5-sulfanylidene-3,7a-dihydro-1H-imidazo[1,5-c][1,3]thiazol-7-one by IUPAC nomenclature, provide its molecular formula.
user
C20H19BrN2O3S2
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