You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[6-[4-(5,6-dimethylpyrimidin-4-yl)piperazin-1-yl]pyrimidin-4-yl]cyclobutan-1-amine is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H25N7
assistant