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.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.text.DecimalFormat;
import java.util.StringTokenizer;

public class C {
    private final static long START_TIME=System.currentTimeMillis();
    private final static boolean LOG_ENABLED=true;
    private final static boolean ONLINE_JUDGE = LOG_ENABLED && (System.getProperty("ONLINE_JUDGE") != null);
    private final static String SYSTEM_ENCODING="utf-8";


    private static class Logger{
        private final PrintWriter logWriter=Util.newPrintWriter(System.err,true);
        private final DecimalFormat df=new DecimalFormat("0.000");
        private void message(String type, String message, Object ... params){
            if(ONLINE_JUDGE){
                return;
            }
            logWriter.printf("["+type+"] "+df.format((System.currentTimeMillis()-START_TIME)/1000.0)+": "+message+"\r\n", params);
        }
        public void debug(String message, Object ... params){
            message("DEBUG", message, params);
        }
    }

    private final static class Util{
        public static PrintWriter newPrintWriter(OutputStream out, boolean autoFlush){
            try {
                return new PrintWriter(new OutputStreamWriter(new BufferedOutputStream(out), SYSTEM_ENCODING),autoFlush);
            } catch (UnsupportedEncodingException e) {
                throw new IllegalStateException(e);
            }
        }
    }

    public final static class FastScanner{
        private BufferedReader reader;
        private StringTokenizer currentTokenizer;
        public FastScanner(Reader reader) {
            if(reader instanceof BufferedReader){
                this.reader=(BufferedReader) reader;
            }else{
                this.reader=new BufferedReader(reader);
            }
        }

        public String next(){
            if(currentTokenizer==null || !currentTokenizer.hasMoreTokens()){
                try {
                    currentTokenizer=new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new IllegalStateException(e);
                }
            }

            return currentTokenizer.nextToken();
        }
        public int nextInt(){
            return Integer.parseInt(next());
        }

        public long nextLong(){
            return Long.parseLong(next());
        }

        public double nextDouble(){
            return Double.parseDouble(next());
        }

    }

    private final static Logger log=new Logger();
    private final BufferedReader reader;
    private final FastScanner in;
    private final PrintWriter out=Util.newPrintWriter(System.out,false);

    public C(BufferedReader reader){
        this.reader=reader;
        in=new FastScanner(this.reader);
    }

    public static void main(String[] args) throws IOException {
        log.debug("Started");
        try{
            new C(new BufferedReader(new InputStreamReader(System.in, SYSTEM_ENCODING))).run();
        }finally{
            log.debug("Stopped");
        }
    }

    void run(){
        solve();
        out.flush(); 
    }

    private void solve(){
        int n = in.nextInt(); 
        int m = in.nextInt();
        int vs[]=new int[n];
        double result=0;
        for(int i=0;i<n;i++){
            vs[i]=in.nextInt();
        }
        for(int i=0;i<m;i++){
            int a=in.nextInt()-1;
            int b=in.nextInt()-1;
            int c=in.nextInt();
            int va = vs[a];
            int vb = vs[b];
            result=Math.max(result, 1.0*(va+vb)/c);
        }
        out.println(result);
    }

}