You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule 5-hydroxy-4,6-dioxo-3-(2-propoxyethyl)-1-(thiophen-3-ylmethyl)-2H-pyrido[2,1-f][1,2,4]triazine-7-carboxylic acid ?
user
C18H21N3O6S
assistant