You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 3-[4-(butan-2-ylamino)-7-methyl-2-(3-methylimidazol-4-yl)quinolin-6-yl]prop-2-enenitrile by IUPAC nomenclature, provide its molecular formula.
user
C21H23N5
assistant