You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[4-(3-fluorophenyl)sulfonylpiperazin-1-yl]-2-[(5-methylthiophen-2-yl)methyl-propan-2-ylamino]ethanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H28FN3O3S2
assistant