Question: which leader in 1943 wanted to open a second front in europe during the war against germany
[{'answer': 'Stalin', 'provenance': [{'wikipedia_id': '70381', 'title': 'Tehran Conference', 'start_paragraph_id': 1, 'start_character': 74, 'end_paragraph_id': 1, 'end_character': 80, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '70381', 'title': 'Tehran Conference', 'start_paragraph_id': 7, 'start_character': 0, 'end_paragraph_id': 7, 'end_character': 232, 'bleu_score': 0.9517713210466091, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15662919097986108093}, 'section': 'Section::::Proceedings.\n'}]}]