You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[[4-(2-methoxyethylamino)phenyl]methyl]-3-[2-(2-methoxyphenyl)ethyl]-2-methylguanidine;hydroiodide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H31IN4O2
assistant