You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 2-[2-[4-(benzenesulfonyl)piperazin-1-yl]-2-oxoethyl]-5,6-diethyl-3-oxopyridazine-4-carbonitrile into its molecular formula.
user
C21H25N5O4S
assistant