Given two lists of integers, return a list containing elements that are in the first list but NOT in the second list. Maintain the order from the first list. Duplicates in the first list should appear once in the result if they are not in the second list.

Examples:

Input: list1 = [1, 2, 3, 4, 5], list2 = [3, 4, 5, 6, 7] Output: [1, 2] Explanation: Elements 1 and 2 are in list1 but not in list2 Input: list1 = [1, 1, 2, 2], list2 = [1] Output: [2] Explanation: Element 1 is excluded, element 2 appears once in result Input: list1 = [5, 10, 15], list2 = [] Output: [5, 10, 15] Explanation: Empty list2 means all elements from list1 are included
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