You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 4-(5-chlorothiophen-2-yl)-N-ethyl-4-oxo-N-[2-oxo-2-(propan-2-ylamino)ethyl]butanamide by IUPAC nomenclature, provide its molecular formula.
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C15H21ClN2O3S
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