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 3-ethyl-7-[4-([1,3]thiazolo[5,4-b]pyridin-2-yl)piperazine-1-carbonyl]-1H-quinazoline-2,4-dione .
user
C21H20N6O3S
assistant