You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-isoquinolin-3-ylspiro[1-azabicyclo[3.2.1]octane-6,5'-4H-1,3-oxazole]-2'-amine is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H20N4O
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