You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (3S,4R)-1-[(3aR,4S,5R,7aS)-5-[(E)-but-1-enyl]-2,3,3a,4,5,7a-hexahydro-1H-inden-4-yl]-4-aminopentan-3-ol into molecular formula.
user
C18H31NO
assistant