#include<bits/stdc++.h>
using namespace std;
#define inf INT_MAX
#define INF LLONG_MAX
#define ll long long
#define ull unsigned long long
#define M (int)(1e9+7)
#define P pair<int,int>
#define FOR(i,m,n) for(int i=(int)m;i<(int)n;i++)
#define RFOR(i,m,n) for(int i=(int)m;i>=(int)n;i--)
#define rep(i,n) FOR(i,0,n)
#define rrep(i,n) RFOR(i,n,0)
#define all(a) a.begin(),a.end()
const int vx[4] = {0,1,0,-1};
const int vy[4] = {1,0,-1,0};
#define F first
#define S second
#define PB push_back
#define EB emplace_back
#define int ll
#define vi vector<int>
#define IP pair<int,P>
#define PI pair<P,int>
#define PP pair<P,P>
#define Yes(f){cout<<(f?"Yes":"No")<<endl;}
#define YES(f){cout<<(f?"YES":"NO")<<endl;}
#define MPlus(x,y) {x=(x+y)%M;}
#define MSub(x,y) {x=(x-y+M)%M;}
#define MMul(x,y) {x=(x*y)%M;}



template< typename T >
struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }

  operator int() const { return to; }
};

template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WG = vector< Edges< T > >;
using UG = vector< vector< int > >;
template< typename T >
using Matrix = vector< vector< T > >;


signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout<<fixed<<setprecision(20);

  int n,m,k;
  cin>>n>>m>>k;
  WG<int> es(n);
  rep(i,m){
    int a,b,c;
    cin>>a>>b>>c;
    a--;b--;
    es[a].PB(edge<int>(b,c));
    es[b].PB(edge<int>(a,c));
  }

  vi d(k);
  rep(i,k){
    cin>>d[i];
  }


  set<int> ans;
  rep(s,n){
    queue<P> q;
    q.push(P(s,0));
    while(q.size()){
      P p=q.front(); q.pop();
      int x=p.F,l=p.S;
      if(l==k){
        ans.insert(x);
        continue;
      }
      for(auto e:es[x]){
        if(e.cost==d[l]){
          q.push(P(e.to,l+1));
        }
      }
    }
  }

  cout<<ans.size()<<endl;
  for(int x:ans){
    cout<<x+1<<' ';
  }
  cout<<endl;




}