#include <algorithm>
#include <ctime>
#include <functional>
#include <iostream>
#include <map>
#include <new>
#include <set>
#include <ostream>
#include <queue>
#include <vector>

using namespace std;

using ld = long double;
using ll = long long;
using ull = unsigned long long;

template <class T> using pq = priority_queue<T>;
template <class T> using pqg = priority_queue<T, vector<T>, greater<T>>;

const long long MOD = 998244353;

bool rec(vector<vector<pair<int,int>>> &g, vector<int>& d, int idx, int v) {
  if (idx == d.size()) return true;

  bool ret = false;
  for (auto [to, w] : g[v]) {
    if (d[idx] != w) continue;
    ret |= rec(g, d, idx + 1, to);
  }

  return ret;
}

int main(void) {
  int n, m, k;
  cin >> n >> m >> k;

  vector<vector<pair<int,int>>> g(n);
  for (int i = 0; i < m; ++i) {
    int u, v, w;
    cin >> u >> v >> w;

    g[u - 1].push_back({v - 1, w});
    g[v - 1].push_back({u - 1, w});
  }

  vector<int> d(k);
  for (int i = 0; i < k; ++i) cin >> d[i];

  reverse(begin(d), end(d));

  vector<int> ans;
  for (int i = 0; i < n; ++i) {
    if (rec(g, d, 0, i)) {
      ans.push_back(i);
    }
  }

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

  return 0;
}