#include <iostream>
#include <queue>
#include <vector>
#include <utility>
#include <algorithm>

#define DBG(x) cerr << x << endl

using namespace std;

class Graph{
	public:
		vector<pair<int, int> >edges;
		vector<int> cost_dp;
		Graph(){
		}
		Graph(const Graph &g){
		}
		void setEdge(int id, int cost){
			edges.push_back(make_pair(id, cost));
		}
};

vector<Graph> g;
vector<int> d;
vector<int> result;
// queue((int city, int count_move));
queue<pair<int, int> > q;

void bfs(){
	for(int i=0; i<g.size(); i++){
		q.push(make_pair(i, 0));
	}
	while(!q.empty()){
		int id = q.front().first;
		int cost_id = q.front().second;
		int cost = d[cost_id];
		q.pop();
		if(!g[id].cost_dp.empty() && g[id].cost_dp.back() == cost){
		//if(binary_search(g[id].cost_dp.begin(), g[id].cost_dp.end(), cost)){
			continue;
		}
		for(int i=0; i<g[id].edges.size(); i++){
			if(g[id].edges[i].second == cost){
				if(g[g[id].edges[i].first].cost_dp.empty() || g[g[id].edges[i].first].cost_dp.back() != cost){

					g[g[id].edges[i].first].cost_dp.push_back(cost_id+1);
					q.push(make_pair(g[id].edges[i].first, cost_id+1));
					if(cost_id+1 == d.size()){
						result.push_back(g[id].edges[i].first);
					}
				}
			}
		}
	}
}

int main(){
	int n,m,k;
	cin >> n >> m >> k;

	for(int i=0; i<=m; i++){
		g.push_back(Graph());
	}
	for(int i=0; i<m; i++){
		int a, b, c;
		cin >> a >> b >> c;
		g[a].setEdge(b, c);
		g[b].setEdge(a, c);
	}

	for(int i=0; i<k; i++){
		int tmp;
		cin >> tmp;
		d.push_back(tmp);
	}

/*
	for(int i=0; i<g.size(); i++){
		for(int ii=0; ii<g[i].edges.size(); ii++){
			DBG(g[i].edges[ii].first);
			DBG(g[i].edges[ii].second);
			DBG("");
		}
	}
*/

	bfs();
	cout << result.size() << endl;
	for(int i=0; i<result.size(); i++){
		cout << result[i] << " ";
	}
	cout << endl;

}