You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
ethyl 4-[[2-[4-(5-bromo-1,3-dioxoisoindol-2-yl)butanoyloxy]acetyl]amino]butanoate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H23BrN2O7
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