You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 9-[(4-chlorophenyl)methyl]-9,11,17-triazatetracyclo[8.7.0.02,7.011,16]heptadeca-1(10),2,4,6,12,14,16-heptaen-8-one by IUPAC nomenclature, provide its molecular formula.
user
C21H14ClN3O
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