#include <iostream>
#include <vector>
#include <list>
using namespace std;

int N, M, K;
vector<list<pair<int, int>>> fee(105);
int d[1010];

bool check(int town, int di) {

    for (auto& p: fee[town]) {
        if (p.second == d[di]) {
            if (di == 0) return true;
            if (check(p.first, di-1)) return true;
        }
    }
    return false;
}

int main() {
    int a, b, c;

    cin >> N >> M >> K;
    for (int i = 0; i < M; i++) {
        cin >> a >> b >> c;
        fee[a].push_back(make_pair(b, c));
        fee[b].push_back(make_pair(a, c));
    }
    for (int i = 0; i < K; i++) {
        cin >> d[i];
    }

    vector<int> t;
    for (int i = 1; i <= N; i++) {
        if (check(i, K-1)) t.push_back(i);
    }

    cout << t.size() << "\n" << t[0];
    for (int i = 1; i < t.size(); i++) {
        cout << " " << t[i];
    }

    return 0;
}