You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(5-ethyl-3,3a,4,6,7,7a-hexahydro-2H-pyrrolo[3,2-c]pyridin-1-yl)ethanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C11H20N2O
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