You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 3-[6-[[1-(aminomethyl)-2-azabicyclo[3.1.1]heptan-2-yl]methyl]-3-oxo-1H-isoindol-2-yl]piperidine-2,6-dione by IUPAC nomenclature, provide its molecular formula.
user
C21H26N4O3
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