You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-(2-cyanoethyl)-1-(2-fluorophenyl)-N-(1H-indol-3-yl)-6-methoxy-2-oxido-2H-isoquinolin-2-ium-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C28H23FN4O3
assistant