#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <functional>
#include <map>
#include <iomanip>
#include <math.h> 
#include <stack>
#include <queue>
#include <bitset>
#include <cstdlib>
#include <tuple>
#include <cctype>
#include <ctype.h>
#include <set>
#include <sstream>
#include <time.h>
using namespace std;
//#define int long long
#define rep(i,s,n) for(int i = s;i<n;i++)
#define repe(i,s,n) for(int i = s;i<=n;i++)
#define rrep(i,s,n) for(int i = (n)-1;i>=(s);i--)
#define all(v) (v).begin(),(v).end()
#define pb push_back
#define fi first
#define se second
#define chmin(a,b) a=min((a),(b))
#define chmax(a,b) a=max((a),(b))
#define l1 list[index]
#define l2 list[index - 1]
#define l3 list[index + 1]
#define iif(i,j) ((i<0 && j<0) || (i>0 && j>0)) ? true : false 
typedef long long ll;
typedef pair<int, int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
typedef pair<pint, int> P1;
typedef pair<int, pint> P2;
typedef pair<pint, pint> PP;
static const ll maxLL = (ll)1 << 62;
const ll MOD = 1000000007;
const ll INF = 1e18;
const double PI = 3.14159265359;
int ca[12] = { 31,28,31,30,31,30,31,31,30,31,30,31 };

struct MyStruct
{
	vector<int>list;
};

int n, m, k, cnt = 0;
map<int, MyStruct>mp;
int klist[2000];
vector<int>anslist;

int func(int index, int no) {

	if (index == k) {
		cnt++;
		anslist.push_back(no);
		return 0;
	}

	bool flag = false;
	for (int i = 0; i < mp[klist[index]].list.size(); i++) {

		if (mp[klist[index]].list[i] > no) break;

		if (mp[klist[index]].list[i] == no) {
			flag = true;
			break;
		}
	}

	if (flag == false) {
		return 0;
	}


	int size = mp[klist[index]].list.size();

	for (int i = 0; i < size; i++) {
		int num = mp[klist[index]].list[i];
		
		if (num == no)continue;

		/*for (int j = 0; j < size; j++) {
			if (i == j)continue;
			int num2 = mp[klist[index]].list[j];*/

			func(index + 1, num);
		//}
	}


	return 0;
}

signed main() {
	

	cin >> n >> m >> k;

	for (int i = 0; i < m; i++) {
		int numa, numb, numc;
		cin >> numa >> numb >> numc;

		if (mp.count(numc) == 0) {
			MyStruct st;
			st.list.push_back(numa);
			st.list.push_back(numb);

			mp.insert(make_pair(numc, st));
		}
		else {
			mp[numc].list.push_back(numa);
			mp[numc].list.push_back(numb);
		}

	}

	for (auto itr = mp.begin(); itr != mp.end(); itr++) {
		sort((*itr).second.list.begin(), (*itr).second.list.end());
	}

	for (int i = 0; i < k; i++) {
		cin >> klist[i];
	}

	for (int i = 0; i < mp[klist[0]].list.size(); i++) {
		func(1, mp[klist[0]].list[i]);
	}
	
	sort(anslist.begin(), anslist.end());

	cout << anslist.size() << endl;

	for (int i = 0; i < anslist.size() - 1; i++) {
		if (anslist[i] != anslist[i + 1]) {
			cout << anslist[i];
		}
		else {
			continue;
		}
		
		//if (i != anslist.size() - 1) {
			cout << " ";
		//}
	}
	//cout << endl;

	cout << anslist[anslist.size() - 1] << endl;
	

	getchar();
	getchar();
	return 0;
}