#include<bits/stdc++.h>  
using namespace std;
typedef long long int64;
struct edge{
  int to, cost;
};
vector< int > visit;
typedef vector< vector< edge > > Graph;
void add_edge(Graph& info, int u, int v, int cost, bool flag = true){
  info[u].push_back( (edge){ v, cost});
  if(flag) info[v].push_back( (edge){ u, cost});
}
bool check(const Graph& graph, const vector< int >& d, int pos, int idx){
  if(pos == -1) return true;
  for(int i = 0; i < graph[idx].size(); i++){
    if(graph[idx][i].cost == d[pos] && check(graph, d, pos - 1, graph[idx][i].to)) return true;
  }
  return false;
}

int main(){
  int N, M, K;
  cin >> N >> M >> K;
  Graph graph(N);
  for(int i = 0; i < M; i++){
    int a, b, c;
    cin >> a >> b >> c;
    add_edge( graph, a - 1, b - 1, c);
  }
  vector< int > d(K);
  for(int i = 0; i < K; i++){
    cin >> d[i];
  }

  for(int i = 0; i < N; i++){
    for(int j = 0; j < graph[i].size(); j++){
      if(graph[i][j].cost == d[K - 1] && check(graph, d, K - 2, graph[i][j].to)){
        visit.push_back(i + 1);
        break;
      }
    }
  }
  cout << visit.size() << endl;
  for(vector< int >::const_iterator it = visit.begin(); it != visit.end(); it++){
    cout << (it == visit.begin() ? "": " ") << *it;
  }
  cout << endl;
}