【cf444A】DZY Loves Physics


DZY loves Physics, and he enjoys calculating density.

Almost everything has density, even a graph. We define the density of a non-directed graph (nodes and edges of the graph have some values) as follows:

where v is the sum of the values of the nodes, e is the sum of the values of the edges.Once DZY got a graph G, now he wants to find a connected induced subgraph G of the graph, such that the density of G is as large as possible.

An induced subgraph G‘(V‘, E‘) of a graph G(V, E) is a graph that satisfies:

  • ;
  • edge  if and only if , and edge ;
  • the value of an edge in G is the same as the value of the corresponding edge in G, so as the value of a node.

Help DZY to find the induced subgraph with maximum density. Note that the induced subgraph you choose must be connected.


The first line contains two space-separated integers n (1 ≤ n ≤ 500). Integer n represents the number of nodes of the graph Gm represents the number of edges.

The second line contains n space-separated integers xi (1 ≤ xi ≤ 106), where xi represents the value of the i-th node. Consider the graph nodes are numbered from 1 to n.

Each of the next m lines contains three space-separated integers ai, bi, ci (1 ≤ ai < bi ≤ n; 1 ≤ ci ≤ 103), denoting an edge between node ai and bi with value ci. The graph won’t contain multiple edges.


Output a real number denoting the answer, with an absolute or relative error of at most 10 - 9.

Sample test(s)







In the first sample, you can only choose an empty subgraph, or the subgraph containing only node 1.

In the second sample, choosing the whole graph is optimal.