You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named methyl 3-[[2-[4-(3-chlorophenyl)piperazin-1-ium-1-yl]acetyl]amino]thiophene-2-carboxylate is given. What is its corresponding molecular formula?
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C18H21ClN3O3S+
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