You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (6R,7R)-8-oxo-3-[(2-oxochromen-7-yl)oxymethyl]-7-(2-oxopropyl)-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid by IUPAC nomenclature, provide its molecular formula.
user
C20H17NO7S
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