You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance [(1R,10S,12R,13Z,14S,16S,17S,18R)-13-ethylidene-14-hydroxy-8,15-diazahexacyclo[14.2.1.01,9.02,7.010,15.012,17]nonadeca-2,4,6,8-tetraen-18-yl] acetate .
user
C21H22N2O3
assistant