You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(2R,3S)-1-(1H-benzimidazol-2-ylamino)-3-methyl-1-oxopentan-2-yl]-4-methoxybenzamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H24N4O3
assistant