Question: when did the continental army leave valley forge
[{'answer': 'June 19 , 1778', 'provenance': [{'wikipedia_id': '10778278', 'title': 'Valley Forge', 'start_paragraph_id': 1, 'start_character': 465, 'end_paragraph_id': 1, 'end_character': 479, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '10778278', 'title': 'Valley Forge', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 695, 'bleu_score': 0.948176576261152, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 477103646729816372}, 'section': 'Section::::Abstract.'}]}]