You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-[7-(1,3-dimethylimidazol-1-ium-2-yl)heptyl]-1,3-dimethylimidazol-1-ium by IUPAC nomenclature, provide its molecular formula.
user
C17H30N4+2
assistant