You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[9-[2-carboxy-4-(3-carboxypropoxy)phenyl]-6-(ethylamino)-2,7-dimethylxanthen-3-ylidene]-ethylazanium is the IUPAC name of a molecule. Please give its molecular formula.
user
C30H33N2O6+
assistant