You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-N-(1-ethylpiperidin-4-yl)-6-N-oxido-2,3,4,9-tetrahydro-1H-carbazole-1,6-diamine The above is the IUPAC name of a molecule. Write its molecular formula.
user
C19H27N4O-
assistant