You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-N-ethyl-6-methyl-2-N-(3-methylphenyl)-4-N-(pyridin-4-ylmethyl)pyrimidine-2,4-diamine The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H23N5
assistant