You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance (3aR,4R,6aS)-1'-(cyclopropylmethyl)-2'-ethyl-N-(2-methylpropyl)-5'-oxospiro[1,3,3a,5,6,6a-hexahydrocyclopenta[c]pyrrole-4,4'-imidazole]-2-carboxamide .
user
C20H32N4O2
assistant