You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(4-bromophenyl)-4-[(4S)-5-ethoxycarbonyl-6-methyl-2-sulfanylidene-3,4-dihydro-1H-pyrimidin-4-yl]pyrazole-3-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
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C18H17BrN4O4S
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