You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-bromo-1-[(2,5-dimethylphenyl)methyl]-3-hydroxy-3-(2-methyl-1H-indol-3-yl)indol-2-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C26H23BrN2O2
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