You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 2-(6-methyl-4-oxo-5-phenylthieno[2,3-d]pyrimidin-3-yl)-N-propan-2-ylacetamide by IUPAC nomenclature, provide its molecular formula.
user
C18H19N3O2S
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