You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[2-(3,4-dichlorophenyl)-2-methylpropyl]-2-methyl-3-(pyridin-2-ylmethyl)guanidine;hydroiodide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H23Cl2IN4
assistant