You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
tert-butyl N-[(2S)-1-(6-bromo-4-chloropyrrolo[2,3-d]pyrimidin-7-yl)but-3-en-2-yl]carbamate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C15H18BrClN4O2
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