#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;

int N, M, K;
vector< pair<int,int> > G[105];
map<pair<int,int>,bool> memo;

bool solve(int x, int idx, const vector<int>& v){
  if(idx >= v.size()) return true;
  if(memo.count(make_pair(x,idx)) > 0) return memo[make_pair(x,idx)];
  
  bool flg = false;
  rep(i,G[x].size()){
    if(G[x][i].first == v[idx]){
      if(solve(G[x][i].second, idx+1, v)){
        flg = true;
      }
    }
  }
  return memo[make_pair(x,idx)] = flg;
}

int main(){
  cin >> N >> M >> K;
  rep(i,M){
    int a, b, c;
    cin >> a >> b >> c;
    a--;
    b--;
    G[a].push_back(make_pair(c,b));
    G[b].push_back(make_pair(c,a));
  }
  vector<int> v;
  rep(i,K){
    int a;
    cin >> a;
    v.push_back(a);
  }
  reverse(ALLOF(v));

  vector<int> ret;
  rep(i,N){
    if(solve(i, 0, v)){
      ret.push_back(i+1);
    }
  }

  cout << ret.size() << endl;
  rep(i,ret.size()){
    if(i!=0) cout << " ";
    cout << ret[i];
  }
  if(ret.size()!=0) cout << endl;
  
  return 0;
}