#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n, m, k;
  cin >> n >> m >> k;
  vector Graph(n, vector<pair<int, int>>(0));
  rep(_, m) {
    int a, b, c;
    cin >> a >> b >> c;
    --a, --b;
    Graph[a].push_back({ b, c });
    Graph[b].push_back({ a, c });
  }
  set<int> cand;
  rep(_, k) {
    int d;
    cin >> d;
    if (_ == 0) {
      rep(i, n) {
        bool ok = false;
        for (auto [__, cost] : Graph[i]) {
          if (cost == d) ok = true;
        }
        if (ok) cand.insert(i);
      }
    }
    else {
      set<int> nCand;
      for (int i : cand) {
        for (auto [j, cost] : Graph[i]) {
          if (cost == d) nCand.insert(j);
        }
      }
      swap(cand, nCand);
    }
  }
  cout << cand.size() << endl;
  for (auto x : cand) cout << x + 1 << ' ';
  cout << endl;
  return 0;
}