Question: when did the winter at valley forge end
[{'answer': '1778', 'provenance': [{'wikipedia_id': '10778278', 'title': 'Valley Forge', 'start_paragraph_id': 1, 'start_character': 474, 'end_paragraph_id': 1, 'end_character': 478, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '10778278', 'title': 'Valley Forge', 'start_paragraph_id': 20, 'start_character': 0, 'end_paragraph_id': 20, 'end_character': 1090, 'bleu_score': 0.9881300380564421, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15121584998503191857}, 'section': 'Section::::Winter quarters.:Supply challenges.\n'}]}]