Question: who sang the original theme song for gilligan's island
[{'answer': 'Sir Lancelot', 'provenance': [{'wikipedia_id': '87639', 'title': "Gilligan's Island", 'start_paragraph_id': 20, 'start_character': 157, 'end_paragraph_id': 20, 'end_character': 169, 'bleu_score': 1.0, 'section': 'Section::::Episodes.:Pilot episode.\n'}]}, {'provenance': [{'wikipedia_id': '87639', 'title': "Gilligan's Island", 'start_paragraph_id': 20, 'start_character': 0, 'end_paragraph_id': 20, 'end_character': 519, 'bleu_score': 0.977397480575333, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11251932577995343675}, 'section': 'Section::::Episodes.:Pilot episode.\n'}]}]