B"You are given n segments on a number line, numbered from 1 to n . The i -th segments covers all integer points from l_i to r_i and has a value w_i . You are asked to select a subset of these segments (possibly, all of them). Once the subset is selected, it's possible to travel between two integer points if there exists a selected segment that covers both of them. A subset is good if it's possible to reach point m starting from point 1 in arbitrary number of moves. The cost of the subset is the difference between the maximum and the minimum values of segments in it. Find the minimum cost of a good subset. In every test there exists at least one good subset. The first line contains two integers n and m ( 1 <= n <= 3 cdot 10^5 ; 2 <= m <= 10^6 ) -- the number of segments and the number of integer points. Each of the next n lines contains three integers l_i , r_i and w_i ( 1 <= l_i < r_i <= m ; 1 <= w_i <= 10^6 ) -- the description of the i -th segment. In every test there exists at least one good subset. Print a single integer -- the minimum cost of a good subset. "...