You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (2R)-2-[(5E)-5-[(4-methoxycarbonylphenyl)methylidene]-4-oxo-2-sulfanylidene-1,3-thiazolidin-3-yl]-3-phenylpropanoic acid by IUPAC nomenclature, provide its molecular formula.
user
C21H17NO5S2
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