You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2S,17S,18S)-17-hydroxy-2,18-dimethyl-17-(trideuteriomethyl)-6,7-diazapentacyclo[11.7.0.02,10.04,8.014,18]icos-4(8)-en-5-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H32N2O2
assistant