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 3-[2-[3-(1-ethyl-3,3,7-trimethylindol-2-ylidene)prop-1-enyl]-3,3,7-trimethylindol-1-ium-1-yl]propanoic acid .
user
C30H37N2O2+
assistant