You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (6S)-6-(2,4-dichlorophenyl)-5-propanoyl-8,9,10,11-tetrahydro-6H-benzo[b][1,4]benzodiazepin-7-one by IUPAC nomenclature, provide its molecular formula.
user
C22H20Cl2N2O2
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