You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1a,2,3,7b-tetrahydro-1H-cyclopropa[a]naphthalen-1-yl-(4-methylpyridin-3-yl)methanamine The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H20N2
assistant