You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(1,1-dioxothiolan-3-yl)-N-[2-methyl-4-(2-methylpiperidine-1-carbonyl)phenyl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H28N2O4S
assistant