You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(6S)-3-(4-fluorophenyl)-6,8-dihydro-5H-imidazo[2,1-c][1,4]oxazin-6-yl]-N-[(6-methoxypyridin-3-yl)methyl]methanamine is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H21FN4O2
assistant