You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (4aS,7aS)-6-(1-pyrazin-2-ylethyl)-1,2,3,4,4a,5,7,7a-octahydropyrrolo[3,4-b]pyridine .
user
C13H20N4
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