You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name N-[4-(6-oxo-3-pyridin-3-ylpyridazin-1-yl)oxolan-3-yl]-4,5,6,7-tetrahydro-2,1-benzoxazole-3-carboxamide into its molecular formula.
user
C21H21N5O4
assistant