You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (1R,2R,3R,4S)-2-N-(3-amino-3-oxopropyl)-3-N-(4-bromophenyl)spiro[bicyclo[2.2.1]hept-5-ene-7,1'-cyclopropane]-2,3-dicarboxamide by IUPAC nomenclature, provide its molecular formula.
user
C20H22BrN3O3
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