You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (3S,3'S,4'R)-6'-bromo-4'-(4-hydroxy-3-methoxyphenyl)-3'-methylspiro[1H-indole-3,2'-3,4-dihydro-1H-quinoline]-2-one by IUPAC nomenclature, provide its molecular formula.
user
C24H21BrN2O3
assistant