#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);++i)
#define all(a) (a).begin(),(a).end()
#define dunk(a) cout << (a) << endl
using namespace std;
typedef long long ll;

int p[1010][110];

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n, m, k;
	cin >> n >> m >> k;
	vector<int> a(1000), b(1000), c(1000), d(1000);
	rep(i, m) cin >> a[i] >> b[i] >> c[i];
	rep(i, k) cin >> d[i];


	for (int i = 0; i < m; ++i) {
		if (d[0] == c[i]) {
			p[0][a[i]] = 1;
			p[0][b[i]] = 1;
		}
	}

	for (int i = 1; i < k; ++i) {
		for (int j = 0; j < m; ++j) {
			if (d[i] == c[j]) {
				if (p[i - 1][a[j]]) p[i][b[j]] = 1;
				if (p[i - 1][b[j]]) p[i][a[j]] = 1;
			}
		}
	}

	int ans = accumulate(p[k - 1], p[k - 1] + 101, 0);
	dunk(ans);

	for (int i = 1; i <= 100; ++i) {
		if (p[k - 1][i]) cout << i << ' ';
	}
	cout << endl;

	return 0;
}