You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2,3-dihydroindol-1-yl-[5-[2-(4-methoxyphenyl)ethylamino]pyrazin-2-yl]methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C22H22N4O2
assistant