You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl (1S,10R,12S,18S)-13-(2-hydroxyethylidene)-8,15-diazapentacyclo[10.5.1.01,9.02,7.010,15]octadeca-2,4,6,8-tetraene-18-carboxylate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H22N2O3
assistant