You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4a-(bromomethyl)-2-hydroxy-5-methyl-3-prop-1-en-2-yl-2,3,4,5,6,7,8,8a-octahydronaphthalen-1-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H23BrO2
assistant