You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (2R)-N-(2-cyanoethyl)-N-methyl-2-(3-methyl-4-oxobenzo[g]quinazolin-2-yl)sulfanylpropanamide into molecular formula.
user
C20H20N4O2S
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