#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <numeric>
#include <cctype>
#include <tuple>
#include <climits>
#include <bitset>
#include <cassert>
#include <random>

#ifdef _MSC_VER
#include <agents.h>
#endif

#define FOR(i, a, b) for(int i = (a); i < (int)(b); ++i)
#define rep(i, n) FOR(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define REV(v) v.rbegin(), v.rend()
#define MEMSET(v, s) memset(v, s, sizeof(v))
#define UNIQUE(v) (v).erase(unique(ALL(v)), (v).end())
#define MP make_pair
#define MT make_tuple

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

int dp[110][1100];

vector<P> G[110];
int val[1100];

int n, m, k;
int rec(int i, int j){
	if (j == k) return 1;

	int &res = dp[i][j];
	if (res >= 0) return res;
	res = 0;
	for (auto p : G[i]){
		if (p.second != val[j]) continue;
		res |= rec(p.first, j + 1);
	}
	return res;
}

int main(){
	cin >> n >> m >> k;
	rep(i, m){
		int a, b, c;
		cin >> a >> b >> c;
		G[a].push_back(MP(b, c));
		G[b].push_back(MP(a, c));
	}

	rep(i, k) cin >> val[k - i - 1];

	MEMSET(dp, -1);
	vector<int> ans;
	rep(i, n + 1) if (rec(i, 0)) ans.push_back(i);

	int nn = ans.size();
	cout << nn << endl;
	rep(i, nn) cout << ans[i] << (i == nn - 1 ? '\n' : ' ');

	return 0;
}