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

struct edge{ int to,cost; };
vector< edge > G[200];

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

  vector<int> ans;
  for(int i = 1; i <= n; i++){
    if(dp[k][i] == true) ans.push_back(i);
  }
  cout << ans.size() << endl;
  for(int u : ans){
    cout << u << " ";
  }
  cout << endl;

  return 0;
}