#include <bits/stdc++.h>
using namespace std;
#define all(c) (c).begin(),(c).end()
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define REP(i,m,n) for(int i=(int)(m);i<(int)(n);i++)
#define rep(i,n) REP(i,0,n)
#define iter(c) __typeof((c).begin())
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
#define pb(a) push_back(a)
#define rd(a) cin>>(a)
#define RD(a,b) cin>>(a)>>(b)
#define pr(a) cout<<(a)<<endl
#define PR(a,b) cout<<(a)<<" "<<(b)<<endl
#define F first
#define S second
#define ll long long
bool check(int n,int m,int x,int y){return (x<0||x>=n||y<0||y>=m)?false:true;}
const ll MAX=1000000007,MAXL=1LL<<60,dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};
typedef pair<ll,ll> P;

int main() {
  int n,m,t;
  cin >> n >> m >> t;
  vector<P> v[n+1];
  rep(i,m) {
    int x,y,z;
    cin >> x >> y >> z;
    v[x].pb(P(y,z));
    v[y].pb(P(x,z));
  }
  int a[t];
  rep(i,t) cin >> a[i];
  set<int> ans;
  bool u[n+1][t+1];
  memset(u,false,sizeof(u));
  REP(i,1,n+1) {
    queue<P> que;
    que.push(P(i,0));
    u[i][0]=true;
    while(!que.empty()) {
      P p=que.front();que.pop();
      int x=p.F,k=p.S;
      if(k==t) {
	ans.insert(x);
	continue;
      }
      rep(j,v[x].size()) {
	if(v[x][j].S==a[k] && !u[v[x][j].F][k+1]) {
	  u[v[x][j].F][k+1]=true;
	  que.push(P(v[x][j].F,k+1));
	}
      }
    }
  }
  pr(ans.size());
  tr(it,ans) {
    if(it!=ans.begin()) cout << " ";
    cout << *it;
  }
  cout << endl;
  return 0;
}