You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Can you give the molecular formula of the molecule 3-(cyclobutadienyl)-9-[(4-methoxypyrimidin-2-yl)oxymethyl]-1,2,4,5-tetrahydro-[1,4]diazepino[1,7-a]benzimidazole ?
user
C21H21N5O2
assistant