You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(3aR,6R,7aS)-1-(3-hydroxypyridine-2-carbonyl)-3a-methoxy-3,4,5,6,7,7a-hexahydro-2H-indol-6-yl]-2-methoxyacetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H25N3O5
assistant