You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 3-[3-[[(6R,7R)-7-(3,4-dichlorophenyl)-1,4-oxazepan-6-yl]methylsulfonyl]phenyl]-4H-1,2,4-oxadiazol-5-one;hydrochloride by IUPAC nomenclature, provide its molecular formula.
user
C20H20Cl3N3O5S
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