You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[2-(4-acetylpiperazin-1-yl)ethyl]-3-[(2R)-1-imidazol-1-ylpropan-2-yl]urea is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H26N6O2
assistant