You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(2-ethylphenyl)-2-[(1S)-3-[(4-methylphenyl)methyl]-2-oxo-1H-imidazo[1,2-a]benzimidazol-1-yl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C27H26N4O2
assistant