You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1R,4S,5R,7aS)-1,5-dimethyl-4-(2-methylprop-1-enyl)-2,4,5,6,7,7a-hexahydro-1H-indene is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H24
assistant