#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>

using namespace std;

struct edge{
	int to;
	int cost;
};

vector<vector<int> > memo;

bool dfs( vector<vector<edge> > &G, vector<int> &d, int pos, int x){
	if(memo[pos][x] >= 0) return memo[pos][x] == 1;
	if( x==0 ){
		return true;
	}
	bool ret = false;
	for(int i=0; i<G[pos].size(); i++){
		if( G[pos][i].cost == d[x-1] ){
			ret |= dfs(G,d, G[pos][i].to, x-1);
		}
		if(ret){
			memo[pos][x] = 1;
			return ret;
		}
	}
	memo[pos][x] = 0;
	return ret;
}


int main(){
	int N,M,K;
	cin >> N >> M >> K;
	vector< vector<edge> > G(N);
	for(int i=0; i<M; i++){
		int a,b,c;
		cin >> a >> b >> c;
		a--;
		b--;
		
		G[a].push_back( (edge){b, c} );
		G[b].push_back( (edge){a, c} );
	}
	
	vector<int> d(K);
	for(int i=0; i<K; i++) cin >> d[i];

	memo = vector<vector<int> >(N, vector<int>(K+1, -1) );

	vector<int> ans;
	for(int i=0; i<N; i++){
		if(dfs(G, d, i, K) == true){
			ans.push_back(i);
		}
	}

	cout << ans.size() << endl;
	for(int i=0; i<ans.size(); i++){
		cout << ans[i]+1 << (i==ans.size()-1?"\n" : " ");
	}
	
	
	return 0;
}