You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl (1R,4aS,8aS)-1-(4-hydroxy-3-oxobutyl)-5,5,8a-trimethyl-1,4,4a,6,7,8-hexahydronaphthalene-2-carboxylate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C19H30O4
assistant