You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[2-(3-methyl-2,3-dihydropyrrolo[2,3-c]pyridin-1-yl)-2-oxoethyl]azepan-2-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C16H21N3O2
assistant