[{"from": "human", "value": "Synthesize a molecule that matches the given characteristics. The molecule is the carbonic salt of calcium (CaCO3). Calcium carbonate is used therapeutically as a phosphate buffer in hemodialysis, as an antacid in gastric hyperacidity for temporary relief of indigestion and heartburn, and as a calcium supplement for preventing and treating osteoporosis. (NCI04)"}, {"from": "gpt", "value": "[C][=Branch1][C][=O][Branch1][C][O-1][O-1].[Ca+2]"}]