You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[5-cyano-4-(oxolan-2-ylmethoxy)pyridin-2-yl]-7-formyl-3,4-dihydro-2H-1,8-naphthyridine-1-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H21N5O4
assistant