#include <bitset>
#include <deque>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <algorithm>
#include <functional>
#include <iterator>
#include <locale>
#include <memory>
#include <stdexcept>
#include <utility>
#include <string>
#include <fstream>
#include <ios>
#include <iostream>
#include <iosfwd>
#include <iomanip>
#include <istream>
#include <ostream>
#include <sstream>
#include <streambuf>
#include <complex>
#include <numeric>
#include <valarray>
#include <exception>
#include <limits>
#include <new>
#include <typeinfo>
#include <cassert>
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <climits>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdlib>
#include <cstddef>
#include <cstdarg>
#include <ctime>
#include <cstdio>
#include <cstring>
#include <cwchar>
#include <cwctype>
using namespace std;
static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);
typedef long long ll;
typedef unsigned long long ull;

#define ALL(c) (c).begin(), (c).end()
#define CLEAR(v) memset(v,0,sizeof(v))
#define MP(a,b) make_pair((a),(b))
#define REP(i,n) for(int i=0;i<(int)n;++i)
#define ABS(a) ((a)>0?(a):-(a))
template<class T> T MIN(const T& a, const T& b) { return a < b ? a : b; }
template<class T> T MAX(const T& a, const T& b) { return a > b ? a : b; }
template<class T> void MIN_UPDATE(T& a, const T& b) { if (a > b) a = b; }
template<class T> void MAX_UPDATE(T& a, const T& b) { if (a < b) a = b; }

int main() {
	std::ios::sync_with_stdio(false);

	int N, M, K;
	cin >> N >> M >> K;
	vector<vector<pair<int, int> > > graph(N + 1);
	REP(m, M) {
		int a, b, c;
		cin >> a >> b >> c;
		graph[a].push_back(MP(b, c));
		graph[b].push_back(MP(a, c));
	}

	bool dp[2][128];
	CLEAR(dp);
	int front = 0;
	int back = 1;
	REP(n, N + 1) {
		dp[back][n] = 1;
	}

	REP(k, K) {
		int d;
		cin >> d;

		REP(n, N + 1) {
			dp[front][n] = false;
		}

		for (int from = 1; from <= N; ++from) {
			for (const auto& edge : graph[from]) {
				if (edge.second != d) {
					continue;
				}

				dp[front][edge.first] |= dp[back][from];
			}
		}

		swap(front, back);
	}

	vector<int> answer;
	REP(n, N) {
		if (dp[back][n + 1]) {
			answer.push_back(n + 1);
		}
	}

	cout << answer.size() << endl;
	REP(i, answer.size()) {
		if (i) {
			cout << " ";
		}
		cout << answer[i];
	}
	cout << endl;
}