You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[3-(2-aminopyrimidin-4-yl)-2-ethoxybenzimidazol-5-yl]-2-(5-methyl-1,2,4-oxadiazol-3-yl)but-3-yn-2-ol is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H19N7O3
assistant