You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (3R,4R)-3-[(2R)-2-(4-chlorophenyl)-2-hydroxyethyl]sulfanyl-1-[4-(5-chloropyridin-3-yl)phenyl]-4-(2,4-dihydroxyphenyl)azetidin-2-one by IUPAC nomenclature, provide its molecular formula.
user
C28H22Cl2N2O4S
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