You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name ethyl 4-[(5E)-5-[(3-ethoxyphenyl)methylidene]-4-oxo-2-sulfanylidene-1,3-thiazolidin-3-yl]butanoate into its molecular formula.
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C18H21NO4S2
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