You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name N-(5-chloro-2-methoxyphenyl)-2-[(4-oxo-5-phenyl-3H-thieno[2,3-d]pyrimidin-2-yl)sulfanyl]acetamide into its molecular formula.
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C21H16ClN3O3S2
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