i need help finding a train leaving cambridge after 15:30 .
{'service': 'train', 'act': 'inform', 'slot_name': 'choice', 'value': '623'} {'service': 'train', 'act': 'request', 'slot_name': 'dest', 'value': '?'}
i found 623 trains that leave at that time . what is your destination ?