You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-(4-bromophenyl)-6-methyl-N-(3-nitrophenyl)-2-sulfanylidene-3,4-dihydro-1H-pyrimidine-5-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H15BrN4O3S
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