CF1015A Points in Segments

You are given a set of $ n $ segments on the axis $ Ox $ , each segment has integer endpoints between $ 1 $ and $ m $ inclusive. Segments may intersect, overlap or even coincide with each other. Each segment is characterized by two integers $ l_i $ and $ r_i $ ( $ 1 \le l_i \le r_i \le m $ ) — coordinates of the left and of the right endpoints. Consider all integer points between $ 1 $ and $ m $ inclusive. Your task is to print all such points that don't belong to any segment. The point $ x $ belongs to the segment $ [l; r] $ if and only if $ l \le x \le r $ .

The first line of the input contains two integers $ n $ and $ m $ ( $ 1 \le n, m \le 100 $ ) — the number of segments and the upper bound for coordinates. The next $ n $ lines contain two integers each $ l_i $ and $ r_i $ ( $ 1 \le l_i \le r_i \le m $ ) — the endpoints of the $ i $ -th segment. Segments may intersect, overlap or even coincide with each other. Note, it is possible that $ l_i=r_i $ , i.e. a segment can degenerate to a point.

In the first line print one integer $ k $ — the number of points that don't belong to any segment. In the second line print exactly $ k $ integers in any order — the points that don't belong to any segment. All points you print should be distinct. If there are no such points at all, print a single integer $ 0 $ in the first line and either leave the second line empty or do not print it at all.

In the first example the point $ 1 $ belongs to the second segment, the point $ 2 $ belongs to the first and the second segments and the point $ 5 $ belongs to the third segment. The points $ 3 $ and $ 4 $ do not belong to any segment. In the second example all the points from $ 1 $ to $ 7 $ belong to the first segment.