You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
cyclobutyl-[1-(imidazol-1-ylmethyl)-5,6,7,9-tetrahydroimidazo[1,5-a][1,4]diazepin-8-yl]methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C16H21N5O
assistant