#include<bits/stdc++.h>
using namespace std;
#define int long long

struct edge{ int to,cost; };
const int N = 2e3+10;
vector< edge > G[N];

signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n,m,k; cin >> n >> m >> k;
  for(int i = 0; i < m; i++){
    int a,b,c; cin >> a >> b >> c;
    G[a].push_back({b,c});
    G[b].push_back({a,c});
  }

  vector<int> dp[N];
  for(int i = 1; i <= n; i++) dp[0].push_back(i);
  for(int i = 0; i < k; i++){
    int d; cin >> d;
    for(int u : dp[i]){
      for(auto v : G[u]){
        if(v.cost == d){
          dp[i+1].push_back(v.to);
        }
      }
    }
  }

  cout << dp[k].size() << endl;
  for(int u : dp[k]){
    cout << u << " ";
  }
  cout << endl;

  return 0;
}