You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 3-[3-[[3-[2-[6,8-bis(sulfanyl)octanoylamino]ethylsulfanyl]-2-methylpropanoyl]amino]propyl-methylamino]propane-1-sulfonic acid by IUPAC nomenclature, provide its molecular formula.
user
C21H43N3O5S4
assistant