You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[2-(4-bromophenyl)-2-oxoethyl]-5-(3,5-dichlorophenyl)-1,6a-dihydropyrrolo[3,4-c]pyrrole-4,6-dione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H13BrCl2N2O3
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