You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (13S,13aR)-2,9,10-trimethoxy-13-methyl-6,8,13,13a-tetrahydro-5H-isoquinolino[2,1-b]isoquinolin-3-ol;hydrochloride into molecular formula.
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C21H26ClNO4
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