You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-(2-fluorophenyl)-2,4,7,8,9,10-hexahydroisochromeno[3,4-f][1,3]benzoxazin-6-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H18FNO3
assistant