#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <set>
#include <map>
#include <sstream>
using namespace std;

#define FOR(i, s, e) for (int i = (s); i <= (e); i++)


int N;
int M;
int K;

struct edge{
    int a;
    int b;
    int cost;
};

edge edges[1000];

int d[1000];

bool dp[1010][110];


int main()
{
    cin >> N >> M >> K;

    FOR(i,0,M - 1)
    {
        edge & e = edges[i];
        cin >> e.a >> e.b >> e.cost;
    }

    FOR(i,1,K)
    {
        cin >> d[i];
    }

    FOR(i,0,1009)
    {
        FOR(j,0,109)
        {
            dp[i][j] = false;
        }
    }

    FOR(i,0,109)
    {
        dp[0][i] = true;
    }

    FOR(i,1,K)
    {
        for(edge e : edges)
        {
            if(e.cost == d[i])
            {
                if(dp[i - 1][e.b])
                    dp[i][e.a] = true;
                if(dp[i - 1][e.a])
                    dp[i][e.b] = true;
            }
        }
    }

    stringstream result;
    int cou = 0;

    FOR(i,1,N)
    {
        if(dp[K][i])
        {
            result << i << " ";
            cou++;
        }
    }

    cout << cou << endl;
    cout << result.str() << endl;
    return 0;
}