You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[4-(1,3-dihydroisoindol-2-yl)-4-oxobutyl]-2-methyl-3-(2-phenylsulfanylpropyl)guanidine;hydroiodide is the IUPAC name of a molecule. Please give its molecular formula.
user
C23H31IN4OS
assistant