i need a train that leaves cambridge at 21:30 i want to go to london liverpool street
and what is your destination for that trip ?
{'service': 'train', 'act': 'inform', 'slot_name': 'choice', 'value': '14'} {'service': 'train', 'act': 'request', 'slot_name': 'day', 'value': '?'}
i found 14 trains . what day do you want to travel ?