Skyline

Given N rectangular buildings, compute the skyline formed by their union. Each building is described by its left x-coordinate L, height H, and right x-coordinate R, and all buildings stand on the same ground line.

The skyline is the outer outline of the rectangles when they are viewed together. Report every point where the visible height changes, from left to right.

The first line contains the number of buildings N (1 <= N <= 100,000).

Each of the next N lines contains three integers L, H, and R, describing one building's left x-coordinate, height, and right x-coordinate.

The coordinates and heights satisfy 1 <= L < R <= 1,000,000,000 and 1 <= H <= 1,000,000,000.

Print the skyline on one line. For each point where the height changes, print the x-coordinate of that point followed by the height from that point onward. Separate all values with spaces.