You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 7,7-dimethyltetracyclo[11.2.2.12,6.18,12]nonadeca-1(16),2(19),3,5,8,10,12(18),13(17),14-nonaene-5,9-diamine into molecular formula.
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C21H20N2
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