You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule (6-methyl-4-oxopyrido[1,2-a]pyrimidin-2-yl)methyl 4-fluoro-3-methyl-1-benzothiophene-2-carboxylate into molecular formula.
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C20H15FN2O3S
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