[{"from": "human", "value": "Generate a molecule based on the given description. The molecule is a polyunsaturated long-chain fatty acid with an 18-carbon backbone and exactly three double bonds. At least 17 different isomers of this compound are recognized."}, {"from": "gpt", "value": "[C][C][C][C][C][C][C][C][C][C][C][/C][=C][/C][=C][/C][=C][/C][=Branch1][C][=O][O]"}]