Question: who were the main countries involved in the cold war
[{'answer': 'Soviet Union', 'provenance': [{'wikipedia_id': '325329', 'title': 'Cold War', 'start_paragraph_id': 1, 'start_character': 62, 'end_paragraph_id': 1, 'end_character': 74, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'United States', 'provenance': [{'wikipedia_id': '325329', 'title': 'Cold War', 'start_paragraph_id': 1, 'start_character': 129, 'end_paragraph_id': 1, 'end_character': 142, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]