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

vector<int> ans;

void solve(int now, int count, map<int, vector<pair<int, int>>>& mm, vector<int>& d){
	for(int i = 0; i < mm[now].size(); i++) if(mm[now][i].second == d[count]){
		if(count + 1 == d.size()) ans.emplace_back(mm[now][i].first);
		else solve(mm[now][i].first, count + 1, mm, d);
	}
}

int main(){
	int n, m, k;
	cin >> n >> m >> k;
	map<int, vector<pair<int, int>>> mm;
	while(m--){
		int a, b, c;
		cin >> a >> b >> c;
		a--; b--;
		mm[a].emplace_back(make_pair(b, c));
		mm[b].emplace_back(make_pair(a, c));
	}
	vector<int> d(k);
	for(auto& dd:d) cin >> dd;
	for(auto itr = mm.begin(); itr != mm.end(); itr++) solve(itr->first, 0, mm, d);
	sort(ans.begin(), ans.end());
	ans.erase(unique(ans.begin(), ans.end()), ans.end());
	cout << ans.size() << endl;
	for(auto& a:ans) cout << a + 1 << ' ';
	cout << endl;
}