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:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Collection;
import java.util.Locale;
import java.util.StringTokenizer;

public class Main {
	public static void main(String[] args) throws IOException {
		new Thread(null, new Runnable() {
			public void run() {
				try {
					long prevTime = System.currentTimeMillis();
					new Main().run();
					System.err.println("Total time: "
							+ (System.currentTimeMillis() - prevTime) + " ms");
					System.err.println("Memory status: " + memoryStatus());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}, "1", 1L << 24).start();
	}

	void run() throws IOException {
		in = new BufferedReader(new InputStreamReader(System.in));
		out = new PrintWriter(System.out);
		Object o = solve();
		if (o != null)
			out.println(o);
		out.close();
		in.close();
	}
	
	private Object solve() throws IOException {
		int n = ni();
		int m = ni();
		
		long[] vs = nla(n);

		double ret=0;
		for(int i =0;i<m;i++){
			int u = ni()-1;
			int v = ni()-1;
			double value = nd();
			ret = Math.max(ret, (vs[u]+vs[v])/ value);
		}
		return ret;
	}


	BufferedReader in;
	PrintWriter out;
	StringTokenizer strTok = new StringTokenizer("");

	String nextToken() throws IOException {
		while (!strTok.hasMoreTokens())
			strTok = new StringTokenizer(in.readLine());
		return strTok.nextToken();
	}

	int ni() throws IOException {
		return Integer.parseInt(nextToken());
	}

	long nl() throws IOException {
		return Long.parseLong(nextToken());
	}

	double nd() throws IOException {
		return Double.parseDouble(nextToken());
	}

	int[] nia(int size) throws IOException {
		int[] ret = new int[size];
		for (int i = 0; i < size; i++)
			ret[i] = ni();
		return ret;
	}

	long[] nla(int size) throws IOException {
		long[] ret = new long[size];
		for (int i = 0; i < size; i++)
			ret[i] = nl();
		return ret;
	}

	double[] nda(int size) throws IOException {
		double[] ret = new double[size];
		for (int i = 0; i < size; i++)
			ret[i] = nd();
		return ret;
	}

	String nextLine() throws IOException {
		strTok = new StringTokenizer("");
		return in.readLine();
	}

	boolean EOF() throws IOException {
		while (!strTok.hasMoreTokens()) {
			String s = in.readLine();
			if (s == null)
				return true;
			strTok = new StringTokenizer(s);
		}
		return false;
	}

	void printRepeat(String s, int count) {
		for (int i = 0; i < count; i++)
			out.print(s);
	}

	void printArray(int[] array) {
		for (int i = 0; i < array.length; i++) {
			if (i > 0)
				out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}

	void printArray(long[] array) {
		for (int i = 0; i < array.length; i++) {
			if (i > 0)
				out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}

	void printArray(double[] array) {
		for (int i = 0; i < array.length; i++) {
			if (i > 0)
				out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}

	void printArray(double[] array, String spec) {
		for (int i = 0; i < array.length; i++) {
			if (i > 0)
				out.print(' ');
			out.printf(Locale.US, spec, array[i]);
		}
		out.println();
	}

	void printArray(Object[] array) {
		boolean blank = false;
		for (Object x : array) {
			if (blank)
				out.print(' ');
			else
				blank = true;
			out.print(x);
		}
		out.println();
	}

	@SuppressWarnings("rawtypes")
	void printCollection(Collection collection) {
		boolean blank = false;
		for (Object x : collection) {
			if (blank)
				out.print(' ');
			else
				blank = true;
			out.print(x);
		}
		out.println();
	}

	static String memoryStatus() {
		return (Runtime.getRuntime().totalMemory()
				- Runtime.getRuntime().freeMemory() >> 20)
				+ "/" + (Runtime.getRuntime().totalMemory() >> 20) + " MB";
	}

	public void pln() {
		out.println();
	}

	public void pln(int arg) {
		out.println(arg);
	}

	public void pln(long arg) {
		out.println(arg);
	}

	public void pln(double arg) {
		out.println(arg);
	}

	public void pln(String arg) {
		out.println(arg);
	}

	public void pln(boolean arg) {
		out.println(arg);
	}

	public void pln(char arg) {
		out.println(arg);
	}

	public void pln(float arg) {
		out.println(arg);
	}

	public void pln(Object arg) {
		out.println(arg);
	}

	public void p(int arg) {
		out.print(arg);
	}

	public void p(long arg) {
		out.print(arg);
	}

	public void p(double arg) {
		out.print(arg);
	}

	public void p(String arg) {
		out.print(arg);
	}

	public void p(boolean arg) {
		out.print(arg);
	}

	public void p(char arg) {
		out.print(arg);
	}

	public void p(float arg) {
		out.print(arg);
	}

	public void p(Object arg) {
		out.print(arg);
	}

}