You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(6-bromo-3-ethyl-4-oxoquinazolin-2-yl)sulfanyl-N-(2,3-dihydro-1,4-benzodioxin-6-yl)propanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H20BrN3O4S
assistant