You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule [2-(2-methylpropyl)-5-oxo-[1,3,4]thiadiazolo[3,2-a]pyrimidin-7-yl]methyl 2-phenoxyacetate into molecular formula.
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C18H19N3O4S
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