You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-(4-cyclobutylpiperazin-1-yl)-2-[4-(5-methylpyridin-2-yl)piperazin-1-yl]ethanone by IUPAC nomenclature, provide its molecular formula.
user
C20H31N5O
assistant