You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Name the molecular formula for the molecule established as N-(3,4-dimethoxyphenyl)-2-[(5-oxo-6-phenyl-4H-1,2,4-triazin-3-yl)sulfanyl]butanamide using the IUPAC nomenclature.
user
C21H22N4O4S
assistant