You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (1R,9R,10R,11R,12Z,17R)-12-ethylidene-9-hydroxy-8,14-diazapentacyclo[9.5.2.01,9.02,7.014,17]octadeca-2,4,6-triene-10-carbonitrile by IUPAC nomenclature, provide its molecular formula.
user
C19H21N3O
assistant