You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3R,8S)-16-ethyl-11-[(1-oxidopyridin-1-ium-3-yl)methyl]-10-oxa-2,11,13,14,18,19-hexazatetracyclo[10.6.1.03,8.013,17]nonadeca-1(18),12(19),14,16-tetraene The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H25N7O2
assistant