#include <bits/stdc++.h>
using namespace std;
vector<vector<pair<int, int>>> g;
vector<int> info;
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);  
	int n, m, k;
	cin >> n >> m >> k;
	g.resize(n);
	for(int i = 0; i < m; i++) {
		int a, b, c;
		cin >> a >> b >> c;
		a--;
		b--;
		g[a].emplace_back(b, c);
		g[b].emplace_back(a, c);
	}
	info.resize(k);
	for(int i = 0; i < n; i++) {
		cin >> info[i];
	}
	reverse(info.begin(), info.end());
	vector<int> ans;
	for(int i = 0; i < n; i++) {
		int cur = i;
		bool ok = true;
		for(int j = 0; j < k; j++) {
			int d = info[j];
			bool found = false;
			for(int l = 0; l < g[cur].size(); l++) {
				int nxt = g[cur][l].first;
				int dd = g[cur][l].second;
				if(dd == d) {
					cur = nxt;
					found = true;
					break;
				} 
			}
			if(!found) {
				ok = false;
				break;
			}
		}
		if(ok) ans.push_back(i);
	}
	cout << ans.size() << endl;
	for(int i = 0; i< ans.size(); i++) {
		if(i > 0) cout << " ";
		cout << ans[i] + 1;
	}
	cout << endl;
	return 0;
}