You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance 2-(4-benzyl-7,8-dichloro-1-ethyl-4,9-dihydro-3H-pyrano[3,4-b]indol-1-yl)acetic acid .
user
C22H21Cl2NO3
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