You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4aS,7aR)-4-(furan-2-ylmethyl)-1,2,3,4a,5,6,7,7a-octahydrocyclopenta[b]pyrazine is the IUPAC name of a molecule. Please give its molecular formula.
user
C12H18N2O
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