You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 5-chloro-N-methyl-2-[[2-oxo-2-[4-(thiophene-2-carbonyl)piperazin-1-yl]ethyl]amino]benzamide by IUPAC nomenclature, provide its molecular formula.
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C19H21ClN4O3S
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