You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[3-methyl-1-[7-[(E)-2-methylbut-2-enyl]-5,6,8,9-tetrahydro-[1,2,4]triazolo[4,3-d][1,4]diazepin-3-yl]butyl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H31N5O
assistant