You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(3S)-3-(imidazol-1-ylmethyl)piperidin-1-yl]-[3-(6-methylpyridazin-3-yl)phenyl]methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H23N5O
assistant