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 N-[4-[(2R)-2-(1H-benzimidazol-2-yl)pyrrolidin-1-yl]-4-oxobutyl]pyrazine-2-carboxamide .
user
C20H22N6O2
assistant