Question: who does the voice of alex in madagascar
[{'answer': 'Ben Stiller', 'provenance': [{'wikipedia_id': '17901688', 'title': 'Madagascar (2005 film)', 'start_paragraph_id': 1, 'start_character': 317, 'end_paragraph_id': 1, 'end_character': 328, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '17901688', 'title': 'Madagascar (2005 film)', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 215, 'bleu_score': 0.948006874591591, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3553110372659101417}, 'section': 'Section::::Voice cast.\n'}]}]