You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(3-benzylsulfonylpropyl)-2-[[2-(difluoromethoxy)phenyl]methyl]-3-ethylguanidine;hydroiodide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H28F2IN3O3S
assistant