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

class Program
{
    static string InputPattern = "InputX";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("3 2 2");
            WillReturn.Add("1 2 10");
            WillReturn.Add("2 3 20");
            WillReturn.Add("10 20");
            //1
            //3
            //犯人は通行料金10の道路を通り、続いて通行料金20の道路を通った。
            //ここから犯人は今町3にいると分かる。
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("3 2 2");
            WillReturn.Add("1 2 10");
            WillReturn.Add("1 2 20");
            WillReturn.Add("10 20");
            //2
            //1 2
            //ある町のペアを複数本の道路が結ぶこともある。
            //また、どの町のペアも互いに行き来できるとは限らない。
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    struct JyoutaiDef
    {
        internal int CurrDInd;
        internal int CurrPos;
    }

    static void Main()
    {
        List<string> InputList = GetInputList();

        int[] wkArr = { };
        Action<string> SplitAct = (pStr) =>
            wkArr = pStr.Split(' ').Select(X => int.Parse(X)).ToArray();

        SplitAct(InputList[0]);
        int N = wkArr[0];
        int M = wkArr[1];

        //隣接行列のListでグラフを定義
        var RinsetuGyouretuListArr = new List<int>[N + 1, N + 1];
        foreach (string EachStr in InputList.Skip(1).Take(M)) {
            SplitAct(EachStr);
            if (RinsetuGyouretuListArr[wkArr[0], wkArr[1]] == null)
                RinsetuGyouretuListArr[wkArr[0], wkArr[1]] = new List<int>();
            if (RinsetuGyouretuListArr[wkArr[1], wkArr[0]] == null)
                RinsetuGyouretuListArr[wkArr[1], wkArr[0]] = new List<int>();

            RinsetuGyouretuListArr[wkArr[0], wkArr[1]].Add(wkArr[2]);
            RinsetuGyouretuListArr[wkArr[1], wkArr[0]].Add(wkArr[2]);
        }
        string wkStr = InputList.ElementAt(1 + M);
        int[] DArr = wkStr.Split(' ').Select(X => int.Parse(X)).ToArray();

        var stk = new Stack<JyoutaiDef>();
        JyoutaiDef WillPush;
        WillPush.CurrDInd = 1;
        for (int I = 0; I <= RinsetuGyouretuListArr.GetUpperBound(0); I++) {
            for (int J = 0; J <= RinsetuGyouretuListArr.GetUpperBound(1); J++) {
                if (RinsetuGyouretuListArr[I, J] == null) continue;
                if (RinsetuGyouretuListArr[I, J].Contains(DArr[0]) == false) continue;
                WillPush.CurrPos = J;
                stk.Push(WillPush);
            }
        }

        var AnswerPosSet = new HashSet<int>();

        while (stk.Count > 0) {
            JyoutaiDef Popped = stk.Pop();
            //Console.WriteLine(Popped.CurrPos);

            //クリア判定
            if (Popped.CurrDInd > DArr.GetUpperBound(0)) {
                AnswerPosSet.Add(Popped.CurrPos);
                continue;
            }

            WillPush.CurrDInd = Popped.CurrDInd + 1;
            for (int J = 0; J <= RinsetuGyouretuListArr.GetUpperBound(1); J++) {
                if (RinsetuGyouretuListArr[Popped.CurrPos, J] == null) continue;
                if (RinsetuGyouretuListArr[Popped.CurrPos, J].Contains(DArr[Popped.CurrDInd]) == false)
                    continue;
                WillPush.CurrPos = J;
                stk.Push(WillPush);
            }
        }
        Console.WriteLine(AnswerPosSet.Count);
        var sb = new System.Text.StringBuilder();
        foreach (int EachInt in AnswerPosSet.OrderBy(X => X)) {
            sb.AppendFormat("{0} ", EachInt);
        }
        Console.WriteLine(sb.ToString().TrimEnd());
    }
}