You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 6-N-(3-chloro-4-methylphenyl)-4-N-ethyl-4-N-(3-methylphenyl)-5-nitropyrimidine-4,6-diamine into its molecular formula.
user
C20H20ClN5O2
assistant