CF1000C Covered Points Count

**题目大意：** 给你n个区间，求被这些区间覆盖层数为$k(k

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The picture describing the first example:  Points with coordinates $ [0, 4, 5, 6, 7, 8] $ are covered by one segment, points $ [1, 2] $ are covered by two segments and point $ [3] $ is covered by three segments. The picture describing the second example:  Points $ [1, 4, 5, 6, 7] $ are covered by one segment, points $ [2, 3] $ are covered by two segments and there are no points covered by three segments.