You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-methyl-4-oxo-N-[1-(5-phenyl-1H-imidazol-2-yl)ethyl]-1,5,6,7-tetrahydroindole-2-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H22N4O2
assistant