#include <iostream>
#include <vector>
#include <algorithm>
#include <sstream>
using namespace std;

template <typename T>
string join(vector<T> v, string str){
	stringstream ss;
	for(int i = 0; i < v.size(); i++){
		if(i) ss << str;
		ss << v[i];
	}
	return ss.str();
}

struct edge{
	int to, cost;
	edge(int to, int cost){
		this->to = to;
		this->cost = cost;
	}
};

int main(){
	int n, m, k;
	cin >> n >> m >> k;
	vector<vector<edge>> e(n);
	while(m--){
		int a, b, c;
		cin >> a >> b >> c;
		a--;
		b--;
		e[a].emplace_back(edge(b, c));
		e[b].emplace_back(edge(a, c));
	}
	int d[k];
	for(int i = 0; i < k; i++) cin >> d[i];
	vector<vector<bool>> puni(k + 1, vector<bool>(n, false));
	for(int i = 0; i < n; i++) puni[0][i] = true;
	for(int i = 1; i <= k; i++) for(int j = 0; j < n; j++) if(puni[i - 1][j]) for(auto& ee:e[j]) if(ee.cost == d[i - 1]) puni[i][ee.to] = true;

	for(int i = 0; i < k + 1; i++){
		for(int j = 0; j < n; j++) cerr << puni[i][j] << ' ';
		cerr << endl;
	}

	vector<int> ans;
	for(int i = 0; i < n; i++) if(puni[k][i]) ans.emplace_back(i + 1);
	cout << ans.size() << endl;
	cout << join(ans, " ") << endl;
}