You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[4-[methyl(propan-2-yl)amino]butyl]-3-[(2-pyrazol-1-ylpyridin-4-yl)methyl]urea by IUPAC nomenclature, provide its molecular formula.
user
C18H28N6O
assistant