You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-(12-chloro-9-methyl-1,8-diazatetracyclo[8.6.1.02,7.014,17]heptadeca-2,4,6,10,12,14(17)-hexaen-8-yl)-2-(dimethylamino)ethanone by IUPAC nomenclature, provide its molecular formula.
user
C20H22ClN3O
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