You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named 6-(2-fluoro-5-methylphenyl)-8-methoxy-N-methyl-2-pyrazin-2-ylquinazolin-4-amine is given. What is its corresponding molecular formula?
user
C21H18FN5O
assistant