#include <iostream>
#include <numeric>
#include <vector>

template <class Cost = int>
struct Edge {
    int src, dst;
    Cost cost;
    Edge(int src = -1, int dst = -1, Cost cost = 1)
        : src(src), dst(dst), cost(cost){};

    bool operator<(const Edge<Cost>& e) const { return this->cost < e.cost; }
    bool operator>(const Edge<Cost>& e) const { return this->cost > e.cost; }
};

template <class Cost = int>
using Graph = std::vector<std::vector<Edge<Cost>>>;

void solve() {
    int n, m, k;
    std::cin >> n >> m >> k;

    Graph<> graph(n);
    while (m--) {
        int u, v, c;
        std::cin >> u >> v >> c;
        --u, --v;
        graph[u].emplace_back(u, v, c);
        graph[v].emplace_back(v, u, c);
    }

    std::vector<bool> dp(n, true);
    auto ndp = dp;

    while (k--) {
        int d;
        std::cin >> d;

        std::fill(ndp.begin(), ndp.end(), false);
        for (int v = 0; v < n; ++v) {
            if (!dp[v]) continue;

            for (auto e : graph[v]) {
                if (e.cost == d) ndp[e.dst] = true;
            }
        }

        std::swap(dp, ndp);
    }

    std::cout << std::accumulate(dp.begin(), dp.end(), 0) << std::endl;
    for (int v = 0; v < n; ++v) {
        if (dp[v]) std::cout << v + 1 << " ";
    }
    std::cout << std::endl;
}

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

    solve();

    return 0;
}