You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(4-bromophenyl)methyl]-1-(2,3-dihydro-1,4-benzodioxin-6-yl)-N-methyl-5-oxopyrrolidine-3-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H21BrN2O4
assistant