You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-ethyl-2-(5-methyl-2-thiophen-2-yl-1,3-oxazol-4-yl)-N-[(4-oxo-3H-quinazolin-2-yl)methyl]acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H20N4O3S
assistant