Given N buildings in a x-axis，each building is a rectangle and can be represented by a triple (start, end, height)，where start is the start position on x-axis, end is the end position on x-axis and height is the height of the building. Buildings may overlap if you see them from far away，find the outline of them。
An outline can be represented by a triple, (start, end, height), where start is the start position on x-axis of the outline, end is the end position on x-axis and height is the height of the outline.
Building Outline
Example
Given 3 buildings：
[
[1, 3, 3],
[2, 4, 4],
[5, 6, 1]
]
The outlines are：
[
[1, 2, 3],
[2, 4, 4],
[5, 6, 1]
]
Notice
Please merge the adjacent outlines if they have the same height and make sure different outlines cant overlap on x-axis.
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