You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(4R)-4-(1-benzofuran-2-yl)-4-methyl-2,5-dioxoimidazolidin-1-yl]-N-(2-bromo-4-methylphenyl)acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H18BrN3O4
assistant