You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[2-(cyclobutylmethylsulfamoyl)ethyl]-3-ethyl-2-[3-(4-methoxyphenyl)butyl]guanidine The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H36N4O3S
assistant