i want a train leaving from cambridge .
{'service': 'train', 'act': 'inform', 'slot_name': 'choice', 'value': '566'} {'service': 'train', 'act': 'inform', 'slot_name': 'depart', 'value': 'cambridge'} {'service': 'general', 'act': 'reqmore', 'slot_name': 'none', 'value': 'none'}
okay . i have 566 trains leaving cambridge . can we narrow it down a little ?