#include <algorithm>
#include <cmath>
#include <cstring>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <string>
#include <unordered_map>
#include <vector>

using namespace std;
using ll = long long;

struct Town {
    ll from, to, cost;
};

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int N, M, K;
    bool dp[107][1007];
    for (int i = 0; i < 107; i++) {
        for (int j = 0; j < 1007; j++) {
            if (j == 0) {
                dp[i][j] = true;
            } else {
                dp[i][j] = false;
            }
        }
    }

    cin >> N >> M >> K;

    vector<Town> graph;
    for (int i = 0; i < M; i++) {
        ll a, b, c;
        cin >> a >> b >> c;
        a--;
        b--;
        graph.push_back(Town{a, b, c});
        graph.push_back(Town{b, a, c});
    }

    for (int i = 1; i <= K; i++) {
        ll d;
        cin >> d;
        for (auto t : graph) {
            if (t.cost == d && dp[t.from][i - 1]) {
                dp[t.to][i] = true;
            }
        }
    }

    vector<int> ans;
    for (int i = 0; i < N; i++) {
        if (dp[i][K]) {
            ans.push_back(i);
        }
    }
    cout << ans.size() << endl;
    for (int i = 0; i < ans.size(); i++) {
        if (i > 0) {
            cout << " ";
        }
        cout << (ans[i] + 1);
    }
    cout << endl;

    return 0;
}