You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(1,3-benzodioxol-5-ylmethyl)-1-[(2,5-difluorophenyl)methyl]-3-ethylguanidine;hydroiodide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H20F2IN3O2
assistant