You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [(Z)-5-ethyl-4-[5-methyl-4-(2-methylthiophen-3-yl)-1H-imidazol-2-yl]hept-3-en-2-ylidene]azanium by IUPAC nomenclature, provide its molecular formula.
user
C18H26N3S+
assistant