using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m, k) = (c[0], c[1], c[2]);
        var map = NArr(m);
        var d = NList;
        var ex = Enumerable.Repeat(true, n).ToArray();
        for (var i = 0; i < k; ++i)
        {
            var nex = new bool[n];
            foreach (var road in map)
            {
                if (road[2] != d[i]) continue;
                nex[road[1] - 1] |= ex[road[0] - 1];
                nex[road[0] - 1] |= ex[road[1] - 1];
            }
            ex = nex;
        }
        var ans = new List<int>();
        for (var i = 0; i < n; ++i) if (ex[i]) ans.Add(i + 1);
        WriteLine(ans.Count);
        if (ans.Count > 0) WriteLine(string.Join(" ", ans));
    }
}