You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(9R,10R)-17-(2-ethoxyethyl)-17-azatetracyclo[7.5.3.01,10.02,7]heptadeca-2(7),3,5-trien-5-ol is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H29NO2
assistant