You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-(2,3,3a,4,5,6,7,7a-octahydro-1H-indol-3-ylmethylamino)-2-(2,6-dioxopiperidin-3-yl)isoindole-1,3-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H26N4O4
assistant