pls ignore
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你将得到一个含有整数（X）的非空列表。在这个任务里，你应该返回在此列表中的非唯一元素的列表。要做到这一点，你需要删除所有独特的元素（这是包含在一个给定的列表只有一次的元素）。解决这个任务时，不能改变列表的顺序。例如：[1，2，3，1，3] 1和3是非唯一元素，结果将是...
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