You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 2-[(3Z)-3-[3-[(2-methoxybenzoyl)amino]-4-oxo-2-sulfanylidene-1,3-thiazolidin-5-ylidene]-2-oxoindol-1-yl]acetic acid by IUPAC nomenclature, provide its molecular formula.
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C21H15N3O6S2
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