You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance 5-ethyl-4-methyl-N-[2-[(2R)-4-methyl-2-phenylpiperazin-1-yl]-2-oxoethyl]thiophene-2-carboxamide .
user
C21H27N3O2S
assistant