You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (8R)-7-[(2,4-dimethoxyphenyl)methyl]-3-(2,5-dimethylpyrazol-3-yl)-8-ethynyl-6,8-dihydro-5H-[1,2,4]triazolo[4,3-a]pyrazine by IUPAC nomenclature, provide its molecular formula.
user
C21H24N6O2
assistant