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

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

void dfs(vector<vector<edge>> &v, vector<int> &d, vector<int> &ans, int k, int now, int count = 0){
	if(count == k){
		ans.emplace_back(now + 1);
		return;
	}
	for(edge &e:v[now]){
		if(e.cost == d[count]){
			dfs(v, d, ans, k, e.to, count + 1);
		}
	}
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n, m, k;
	cin >> n >> m >> k;
	vector<vector<edge>> v(n);
	while(m--){
		int a, b, c;
		cin >> a >> b >> c;
		a--;
		b--;
		v[a].emplace_back(edge(b, c));
		v[b].emplace_back(edge(a, c));
	}
	vector<int> d(k);
	for(int &x:d) cin >> x;
	vector<int> ans;
	for(int i = 0; i < n; i++){
		dfs(v, d, ans, k, i);
	}
	sort(ans.begin(), ans.end());
	ans.erase(unique(ans.begin(), ans.end()), ans.end());
	cout << ans.size() << endl;
	for(int x:ans) cout << x << ' ';
	cout << endl;
	return 0;
}