You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named N-[2-fluoro-5-[4-methyl-6-[4-(4-methylpiperazin-1-yl)anilino]-5-oxopyrazin-2-yl]phenyl]formamide by IUPAC nomenclature, provide its molecular formula.
user
C23H25FN6O2
assistant