You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3aR,7aR)-N-[2-(4-hydroxy-3-methoxyphenyl)ethyl]-1,3,3a,4,7,7a-hexahydroisoindole-2-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H24N2O3
assistant