You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[[1-[2-(1,2-benzoxazol-3-yl)acetyl]azetidin-3-yl]methyl]-7,8-dihydro-5H-thiopyrano[4,3-c]pyridazin-3-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20N4O3S
assistant