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5513: The Classic Problem

内存限制：256 MB 时间限制：2 S
题面：传统 评测方式：文本比较 上传者：
提交：6 通过：0
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题目描述

E. The Classic Problem
time limit per test
5 seconds
memory limit per test
768 megabytes
input
standard input
output
standard output
You are given a weighted undirected graph on n vertices and m edges. Find the shortest path from vertex s to vertex t or else state that such path doesn't exist.
Input
The first line of the input contains two space-separated integers − n and m (1≤n≤105; 0≤m≤105).
Next m lines contain the description of the graph edges. The i-th line contains three space-separated integers − ui, vi, xi (1≤ui,vi≤n; 0≤xi≤105). That means that vertices with numbers ui and vi are connected by edge of length 2xi (2 to the power of xi).
The last line contains two space-separated integers − the numbers of vertices s and t.
The vertices are numbered from 1 to n. The graph contains no multiple edges and self-loops.
Output
In the first line print the remainder after dividing the length of the shortest path by 1000000007(109+7) if the path exists, and -1 if the path doesn't exist.
If the path exists print in the second line integer k − the number of vertices in the shortest path from vertex s to vertex t; in the third line print k space-separated integers − the vertices of the shortest path in the visiting order. The first vertex should be vertex s, the last vertex should be vertex t. If there are multiple shortest paths, print any of them.
Examples
Input 
4 4
1 4 2
1 2 0
2 3 0
3 4 0
1 4
Output 
3
4
1 2 3 4
Input 
4 3
1 2 4
2 3 5
3 4 6
1 4
Output 
112
4
1 2 3 4
Input 
4 2
1 2 0
3 4 1
1 4
Output 
-1
Note
A path from vertex s to vertex t is a sequence v0, ..., vk, such that v0=s, vk=t, and for any i from 0 to k-1 vertices vi and vi+1 are connected by an edge.
The length of the path is the sum of weights of edges between vi and vi+1 for all i from 0 to k-1.
The shortest path from s to t is the path which length is minimum among all possible paths from s to t.

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