You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[[(2R,3aR,4S,8aR)-4-hydroxy-1-[[4-hydroxy-1-(3-methoxyphenyl)piperidin-4-yl]methyl]-3a,4-dimethyl-3,5,6,7,8,8a-hexahydro-2H-cyclohepta[b]pyrrol-2-yl]methyl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C27H43N3O4
assistant