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Спектакль преподавателей ЛКШ.июль-2007

Undirected weighted graph is given. Find the weight of the minimal path between two vertices.

Input

The first line contains two numbers n and m (1 ≤ n ≤ 105, 1 ≤ m ≤ 2 * 105) - the number of vertices and edges. Second line contains two numbers s and t (1 ≤ s, t ≤ n, s ≠ t) - the numbers of the vertices the length between which you need to find.

Next m lines contain the description of the edges, one edge in a line. The edge number i is described with three integers bi, ei и wi (1 ≤ bi, ei ≤ n, 0 ≤ wi ≤ 100) - the vertices connected by the edge and its weight.

Output

Print the weight of the minimal path between the vertices s and t, or -1 if there is no such path.