You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-[(4aR,8aS)-1,2,3,4,4a,5,6,7,8,8a-decahydroquinolin-1-ium-1-yl]-N-[[4-(dimethylamino)phenyl]methyl]acetamide by IUPAC nomenclature, provide its molecular formula.
user
C20H32N3O+
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