using System.Linq;
using System.Collections.Generic;
using System;

public struct P
{
    public int from { get; set; }
    public int fee { get; set; }
}

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var m = int.Parse(line[1]);
        var k = int.Parse(line[2]);
        var d = new Dictionary<P, int>();
        for (int i = 0; i < m; i++)
        {
            line = Console.ReadLine().Trim().Split(' ');
            var a = int.Parse(line[0]);
            var b = int.Parse(line[1]);
            var c = int.Parse(line[2]);
            var p0 = new P { from = a, fee = c };
            var p1 = new P { from = b, fee = c };
            d[p0] = b;
            d[p1] = a;
        }
        getAns(n, d);
    }
    static void getAns ( int n, Dictionary<P,int> d)
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var k = Array.ConvertAll(line, int.Parse);
        var ans = Enumerable.Range(1, n).ToList();
        var ans2 = new List<int>();
        foreach(var x in k)
        {
            foreach(var y in ans)
            {
                var p = new P { from = y, fee = x };
                if (d.ContainsKey(p)) ans2.Add(d[p]);
            }
            ans.Clear();
            foreach (var y in ans2) ans.Add(y);
            ans2.Clear();
        }
        ans.Sort();
        Console.WriteLine(ans.Count());
        Console.WriteLine(string.Join(" ",ans));
    }
}