Problem: 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: 

<image> 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:

  * <image>; 
  * edge <image> if and only if <image>, and edge <image>; 
  * 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.

<image>

Input

The first line contains two space-separated integers n (1 ≤ n ≤ 500), <image>. Integer n represents the number of nodes of the graph G, m 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.

Examples

Input

1 0
1


Output

0.000000000000000


Input

2 1
1 2
1 2 1


Output

3.000000000000000


Input

5 6
13 56 73 98 17
1 2 56
1 3 29
1 4 42
2 3 95
2 4 88
3 4 63


Output

2.965517241379311

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.

Solution (in JAVA):

Solution:
/*
 * Remember a 7.0 student can know more than a 10.0 student.
 * Grades don't determine intelligence, they test obedience. 
 * I Never Give Up.
 */
import java.util.*;
import java.io.*;

//import javafx.util.Pair;
import static java.lang.System.out;
import static java.util.Arrays.*;
import static java.lang.Math.*;
public class ContestMain {
	private static Reader in=new Reader();
	private static StringBuilder ans=new StringBuilder();
	private static long MOD=1000000007;//10^9+7 
	private static final int N=1000000;//10^6
//	private static final double PI=3.1415;
	private static ArrayList<Integer> v[]=new ArrayList[N];
//	private static int color[]=new int[N]; //For Graph Coloring
	private static boolean mark[]=new boolean[N];
//	private static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
//	private static void dfs(int node){mark[node]=true;for(int x:v[node]){if(!mark[x]){dfs(x);}}}
	private static long powmod(long x,long n,long m){
		if(n==0)return 1;
		else if(n%2==0)return(powmod((x*x)%m,n/2,m));
		else return (x*(powmod((x*x)%m,(n-1)/2,m)))%m;
	}
	public static void solve(long ar[],int n){
		
	}
	public static void main(String[] args) throws IOException{
		int n=in.nextInt();
		int m=in.nextInt();
		double ar[]=new double[n];
		for(int i=0;i<n;i++)
			ar[i]=in.nextInt();
		double ans=0;
		double ed;
		int x,y;
		while(m-->0){
			x=in.nextInt();
			y=in.nextInt();
			ed=in.nextInt();
//			out.println((ar[x-1]+ar[y-1])/ed);
			ans=max(ans,(ar[x-1]+ar[y-1])/ed);
		}
		out.printf("%.9f",ans);
	}
	static class Reader{
        BufferedReader br;
        StringTokenizer st;
        public Reader()
        {
            br = new BufferedReader(new
                     InputStreamReader(System.in));
        }
 
        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        int nextInt()
        {
            return Integer.parseInt(next());
        }
 
        long nextLong()
        {
            return Long.parseLong(next());
        }
 
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
 
        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
}