i am looking for a train to cambridge that leaves on saturday .
{'service': 'train', 'act': 'inform', 'slot_name': 'depart', 'value': 'london kings cross'} {'service': 'train', 'act': 'inform', 'slot_name': 'day', 'value': 'saturday'} {'service': 'train', 'act': 'inform', 'slot_name': 'dest', 'value': 'cambridge'} {'service': 'train', 'act': 'request', 'slot_name': 'depart', 'value': '?'}
the london kings cross travels to cambridge on saturday . where are you leaving from ?