You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-[[2-[3-[(2R)-butan-2-yl]-4-oxoquinazolin-2-yl]sulfanylacetyl]-ethylamino]-N-ethylacetamide by IUPAC nomenclature, provide its molecular formula.
user
C20H28N4O3S
assistant