You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
6-N-(4-fluorophenyl)-4-N,2-dimethyl-4-N-(2-pyridin-4-ylethyl)pyrimidine-4,6-diamine is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H20FN5
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