You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-(2,3-dihydro-1,4-benzothiazin-4-yl)-N-[(4R)-4-ethyl-2,5-dioxo-4-phenylimidazolidin-1-yl]acetamide by IUPAC nomenclature, provide its molecular formula.
user
C21H22N4O3S
assistant