You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(8aR)-2-methyl-7-(oxane-4-carbonyl)-5,6,8,8a-tetrahydro-1H-imidazo[1,5-a]pyrazin-3-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C13H21N3O3
assistant