【cf444A】DZY Loves Physics

2014年7月7日1,0450

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.

Input

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

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

Sample test(s)
input

output

input

output

input

output

Note

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.

题解

可以发现最优解一定只选取了一条边。。。