You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (2S)-N-[(4R)-3,4-dihydro-2H-chromen-4-yl]-2-(4-oxo-2-sulfanylidene-1H-quinazolin-3-yl)propanamide by IUPAC nomenclature, provide its molecular formula.
user
C20H19N3O3S
assistant