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 2-[[2-(4-pyridin-1-ium-2-ylpiperazin-1-ium-1-yl)acetyl]amino]-4,5,6,7-tetrahydro-1-benzothiophene-3-carboxylate is given. What is its corresponding molecular formula?
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C21H28N4O3S+2
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