You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-bromo-1-[2-[(2S)-6-fluoro-2-methyl-3,4-dihydro-2H-quinolin-1-yl]-2-oxoethyl]indole-3-carbaldehyde is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H18BrFN2O2
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