You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(E)-3-(4-bromophenyl)-N-[2-[[(E)-3-(4-bromophenyl)prop-2-enoyl]amino]propyl]prop-2-enamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H20Br2N2O2
assistant