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 (2Z,5R)-5-(4-chlorophenyl)-2-[1-(4-chlorophenyl)propylidene]-5-ethyl-4-sulfanylidene-1,3-oxathian-6-one is given. What is its corresponding molecular formula?
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C21H18Cl2O2S2
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