You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2-methoxypyridin-3-yl)-spiro[4,9-dihydro-3H-pyrano[3,4-b]indole-1,4'-piperidine]-1'-ylmethanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H23N3O3
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