You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5R)-5-[2-(3,5-dibromopyridin-1-ium-1-yl)acetyl]-5-(2-methylpropyl)oxolan-2-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H18Br2NO3+
assistant