#include <bits/stdc++.h>
using namespace std;

int main() {
    int N, M, K, d[1010];
    vector<pair<int, int>> V[110];
    cin >> N >> M >> K;
    for (int i = 0; i < M; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        a--;
        b--;
        V[a].push_back({b, c});
        V[b].push_back({a, c});
    }
    for (int i = 0; i < K; i++) {
        cin >> d[i];
    }

    vector<bool> possible(N, true);

    for (int i = 0; i < K; i++) {
        vector<bool> nxt(N, false);
        for (int now = 0; now < N; now++) {
            if (possible[now]) {
                for (auto& road : V[now]) {
                    if (road.second == d[i])
                        nxt[road.first] = true;
                }
            }
        }
        possible = nxt;
    }

    vector<int> ans;
    for (int i = 0; i < N; i++) {
        if (possible[i])
            ans.push_back(i + 1);
    }

    cout << (int)ans.size() << endl;
    for (auto& x : ans)
        cout << x << " ";
    cout << endl;
}