CF612D The Union of k-Segments

You are given $ n $ segments on the coordinate axis Ox and the number $ k $ . The point is satisfied if it belongs to at least $ k $ segments. Find the smallest (by the number of segments) set of segments on the coordinate axis Ox which contains all satisfied points and no others.

The first line contains two integers $ n $ and $ k $ ( $ 1

First line contains integer $ m $ — the smallest number of segments. Next $ m $ lines contain two integers $ a_{j},b_{j} $ ( $ a_{j}