Question: who was the president of pakistan during 1971 war
[{'answer': 'President Yahya Khan', 'provenance': [{'wikipedia_id': '464071', 'title': 'Indo-Pakistani War of 1971', 'start_paragraph_id': 6, 'start_character': 293, 'end_paragraph_id': 6, 'end_character': 313, 'bleu_score': 1.0, 'section': 'Section::::Background.\n'}]}, {'answer': 'Yahya Khan', 'provenance': [{'wikipedia_id': '464071', 'title': 'Indo-Pakistani War of 1971', 'start_paragraph_id': 5, 'start_character': 566, 'end_paragraph_id': 5, 'end_character': 576, 'bleu_score': 1.0, 'section': 'Section::::Background.\n'}]}, {'provenance': [{'wikipedia_id': '464071', 'title': 'Indo-Pakistani War of 1971', 'start_paragraph_id': 10, 'start_character': 0, 'end_paragraph_id': 10, 'end_character': 526, 'bleu_score': 0.8860704124195401, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3481251256373039958}, 'section': 'Section::::Background.\n'}]}, {'provenance': [{'wikipedia_id': '464071', 'title': 'Indo-Pakistani War of 1971', 'start_paragraph_id': 21, 'start_character': 21, 'end_paragraph_id': 21, 'end_character': 774, 'bleu_score': 0.7320606478274231, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3481251256373039958}, 'section': "Section::::India's official engagement with Pakistan.:Objective.\n"}]}, {'provenance': [{'wikipedia_id': '464071', 'title': 'Indo-Pakistani War of 1971', 'section': 'Section::::Background.\n', 'start_paragraph_id': 10, 'end_paragraph_id': 10, 'meta': {'evidence_span': ['The Government of Pakistan used the "Bihari massacre" to justify its deployment of the military in East Pakistan on 25 March, when it initiated its military crackdown. President Yahya Khan called on the military', 'President Yahya Khan called on the military - which was overwhelmingly led by West Pakistanis', 'President Yahya Khan']}}]}]