You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(3aR,6aS)-4-oxo-1,2,3,5,6,6a-hexahydropentalen-3a-yl]-4-methyl-2-phenylmethoxypentanamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H29NO3
assistant