#include "bits/stdc++.h"
using namespace std;
#define ll long long int
#define rep(i,n) for( int i = 0; i < n; i++ )
#define rrep(i,n) for( int i = n; i >= 0; i-- )
#define REP(i,s,t) for( int i = s; i <= t; i++ )
#define RREP(i,s,t) for( int i = s; i >= t; i-- )
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define INF 2000000000
#define mod 1000000007
#define INF2 1000000000000000000
#define int long long

vector<int> k;
int N, M, K;
vector<pair<int, int>> d[101];

bool dfs(int a, int cnt) {
	//cout << a << " " << cnt << endl;
	if (cnt == K) return true;
	rep(i, d[a].size()) {
		if (d[a][i].second == k[cnt]) {
			if (dfs(d[a][i].first, cnt + 1)) return true;
		}
	}
	
	return false;
}



signed main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
	cin >> N >> M >> K;
	rep(i, M) {
		int a, b, c;
		cin >> a >> b >> c;
		d[a].push_back({ b, c });
		d[b].push_back({ a, c });
	}
	int x[K] = {};
	rep(i, K) {
		int r; cin >> r;
		x[i] = r;
	}
	rrep(i, K - 1) {
		k.push_back(x[i]);
	}
	vector<int> ans;
	rep(i, N) {
		if (dfs(i + 1, 0)) ans.push_back(i + 1);
	}
	cout << ans.size() << endl;
	rep(i, ans.size()) {
		if (i != 0) cout << " ";
		cout << ans[i];
	}
	cout << endl;





    return 0;
}