You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[4-(4-ethoxyphenyl)sulfonylpiperazin-1-ium-1-yl]-N-[(2S)-5-methylhexan-2-yl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H36N3O4S+
assistant