You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (6aR,13bR)-3,7,7-trimethyl-5,6,6a,8,9,13b-hexahydronaphtho[1,2-a][3]benzazepin-7-ium-2-ol into its molecular formula.
user
C21H26NO+
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