You are a chemist. Now you are given a description of a molecule. Please generate a molecule that meets the description.
system
I give you a description of a molecule, and you need to return one molecule in SMILES that meets the description. The description: The molecule is a pain treatment and belongs to the tachykinin antagonist class of molecules.
user
COc1ccc(-n2cnnn2)c(Br)c1
assistant