You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(3-ethyl-2-oxobenzimidazol-1-yl)-N-[4-[4-(3-methylphenyl)piperazin-1-yl]butan-2-yl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C26H35N5O2
assistant