You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N',N'-dimethyl-N-(6,7,8,9-tetrahydro-5H-benzo[7]annulen-5-yl)propane-1,3-diamine is the IUPAC name of a molecule. Please give its molecular formula.
user
C16H26N2
assistant