You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[(4-ethyl-5-pyrazin-2-yl-1,2,4-triazol-3-yl)sulfanyl]-3-(2-methoxyphenyl)propan-2-one by IUPAC nomenclature, provide its molecular formula.
user
C18H19N5O2S
assistant