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.*;//building towers\
import java.util.*;

/**
 * @author master_j
 * @version 0.4
 * @since May 3, 2014
 */
public class Main {

    private void solve() throws IOException {
        int n = io.nI(), m = io.nI();
        if(m == 0){
            io.wln(0);
            return;
        }
        int[] v = new int[n];
        for(int i = 0; i < n; i++)
            v[i] = io.nI();
        double ans = 0.0d;
        for(int i = 0; i < m; i++){
            double t = 1.0d * (v[io.nI() - 1] + v[io.nI() - 1]) / io.nI();
            ans = Math.max(ans, t);
        }
        io.wf("%.10f\n", ans);
    }//2.2250738585072012e-308

    public static void main(String[] args) throws IOException {
        IO.launchSolution(args);
    }

    Main(IO io) throws IOException {
        this.io = io;
        solve();
    }

    private final IO io;
}

class IO {
    static final String _localArg = "master_j";
    private static final String _problemName = "";
    private static final IO.Mode _inMode = Mode.STD_;
    private static final IO.Mode _outMode = Mode.STD_;
    private static final boolean _autoFlush = false;

    static enum Mode {STD_, _PUT_TXT, PROBNAME_}

    private final StreamTokenizer st;
    private final BufferedReader br;
    private final Reader reader;

    private final PrintWriter pw;
    private final Writer writer;

    static void launchSolution(String[] args) throws IOException {
        boolean local = (args.length == 1 && args[0].equals(IO._localArg));
        IO io = new IO(local);

        long nanoTime = 0;
        if (local) {
            nanoTime -= System.nanoTime();
            io.wln("<output>");
        }

        io.flush();
        new Main(io);
        io.flush();

        if(local){
            io.wln("</output>");
            nanoTime += System.nanoTime();
            final long D9 = 1000000000, D6 = 1000000, D3 = 1000;
            if(nanoTime >= D9)
                io.wf("%d.%d seconds\n", nanoTime/D9, nanoTime%D9);
            else if(nanoTime >= D6)
                io.wf("%d.%d millis\n", nanoTime/D6, nanoTime%D6);
            else if(nanoTime >= D3)
                io.wf("%d.%d micros\n", nanoTime/D3, nanoTime%D3);
            else
                io.wf("%d nanos\n", nanoTime);
        }

        io.close();
    }

    IO(boolean local) throws IOException {
        if(_inMode == Mode.PROBNAME_ || _outMode == Mode.PROBNAME_)
            if(_problemName.length() == 0)
                throw new IllegalStateException("You imbecile. Where's my <_problemName>?");

        if(_problemName.length() > 0)
            if(_inMode != Mode.PROBNAME_ && _outMode != Mode.PROBNAME_)
                throw new IllegalStateException("You imbecile. What's the <_problemName> for?");

        Locale.setDefault(Locale.US);

        if (local) {
            reader = new FileReader("input.txt");
            writer = new OutputStreamWriter(System.out);
        } else {
            switch (_inMode) {
                case STD_:
                    reader = new InputStreamReader(System.in);
                    break;
                case PROBNAME_:
                    reader = new FileReader(_problemName + ".in");
                    break;
                case _PUT_TXT:
                    reader = new FileReader("input.txt");
                    break;
                default:
                    throw new NullPointerException("You imbecile. Gimme _inMode.");
            }
            switch (_outMode) {
                case STD_:
                    writer = new OutputStreamWriter(System.out);
                    break;
                case PROBNAME_:
                    writer = new FileWriter(_problemName + ".out");
                    break;
                case _PUT_TXT:
                    writer = new FileWriter("output.txt");
                    break;
                default:
                    throw new NullPointerException("You imbecile. Gimme _outMode.");
            }
        }

        br = new BufferedReader(reader);
        st = new StreamTokenizer(br);

        pw = new PrintWriter(writer, _autoFlush);

        if(local && _autoFlush)
            wln("Note: auto-flush is on.");
    }

    void wln()          {pw.println(); }
    void wln(boolean x) {pw.println(x);}
    void wln(char x)    {pw.println(x);}
    void wln(char x[])  {pw.println(x);}
    void wln(double x)  {pw.println(x);}
    void wln(float x)   {pw.println(x);}
    void wln(int x)     {pw.println(x);}
    void wln(long x)    {pw.println(x);}
    void wln(Object x)  {pw.println(x);}
    void wln(String x)  {pw.println(x);}

    void wf(String f, Object...o){pw.printf(f, o);}

    void w(boolean x)   {pw.print(x);}
    void w(char x)      {pw.print(x);}
    void w(char x[])    {pw.print(x);}
    void w(double x)    {pw.print(x);}
    void w(float x)     {pw.print(x);}
    void w(int x)       {pw.print(x);}
    void w(long x)      {pw.print(x);}
    void w(Object x)    {pw.print(x);}
    void w(String x)    {pw.print(x);}

    int nI() throws IOException    {st.nextToken(); return (int)st.nval;}
    double nD() throws IOException {st.nextToken(); return st.nval;}
    float nF() throws IOException  {st.nextToken(); return (float)st.nval;}
    long nL() throws IOException   {st.nextToken(); return (long)st.nval;}
    String nS() throws IOException {st.nextToken(); return st.sval;}

    void wc(String x){ wc(x.toCharArray()); }
    void wc(char c1, char c2){for(char c = c1; c<=c2; c++)wc(c);}
    void wc(char x[]){
        for(char c : x)
            wc(c);
    }
    void wc(char x){st.ordinaryChar(x); st.wordChars(x, x);}

    public boolean eof() {return st.ttype == StreamTokenizer.TT_EOF;}
    public boolean eol() {return st.ttype == StreamTokenizer.TT_EOL;}

    void flush(){pw.flush();}
    void close() throws IOException{reader.close(); br.close(); flush(); pw.close();}
}