You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-ethyl-1-[2-[2-(1-ethylpiperidin-1-ium-1-yl)ethoxy]ethyl]piperidin-1-ium;diiodide by IUPAC nomenclature, provide its molecular formula.
user
C18H38I2N2O
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