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

public class Edge
{
    public int to { 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 aa = new List<Edge>[n];
        for (int i = 0; i < n; i++) aa[i] = new List<Edge>();
        for (int i = 0; i < m; i++)
        {
            line = Console.ReadLine().Trim().Split(' ');
            var a = int.Parse(line[0]) - 1;
            var b = int.Parse(line[1]) - 1;
            var c = int.Parse(line[2]);
            aa[a].Add(new Edge { to = b, fee = c });
            aa[b].Add(new Edge { to = a, fee = c });
        }
        getAns(n, m, aa);
    }
    static void getAns(int n, int m, List<Edge>[] aa)
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var k = Array.ConvertAll(line, int.Parse);
        var ans = Enumerable.Range(0, n).ToList();
        foreach (var x in k)
        {
            var ans2 = new List<int>();
            foreach (var y in ans)
            {
                foreach (var z in aa[y])
                {
                    if (z.fee == x) ans2.Add(z.to);
                }
            }
            ans = ans2;
        }
        ans.Sort();
        var ans3 = new List<int>();
        foreach (var x in ans) ans3.Add(x + 1);
        Console.WriteLine(ans3.Count());
        Console.WriteLine(string.Join(" ", ans3));
    }
}