You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 1-[2-(5-fluoro-1H-indol-3-yl)ethyl]-3-[2-(4-fluorophenyl)ethyl]-2-methylguanidine;hydroiodide into its molecular formula.
user
C20H23F2IN4
assistant