#include<iostream>
#include<string>
#include<algorithm>
#include<functional>
#include<vector>
#include<queue>
#include<stack>
#include<set>
#include<map>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
using namespace std;

int n,m,k;
int a,b,c;
int d[1000];

vector<int> to[100];
vector<int> cost[100];

int dp[1001][100];

int main(){
	int i,j,l;
	
	cin >> n >> m >> k;
	for( i = 0; i < m; i++ ){
		cin >> a >> b >> c;
		a--;b--;
		to[a].push_back(b);
		to[b].push_back(a);
		cost[a].push_back(c);
		cost[b].push_back(c);
	}
	for( i = 0; i < k; i++ ){
		cin >> d[i];
	}
	
	for( i = 0; i < n; i++ ){
		dp[0][i] = 1;
	}
	
	for( i = 0; i < k; i++ ){
		for( j = 0; j < n; j++ ){
			//cout << dp[i][j] << " " ;
			if( dp[i][j] == 0 )
				continue;
			for( l = 0; l < to[j].size(); l++ ){
				if( cost[j][l] == d[i] )
					dp[i+1][ to[j][l] ] = 1;
			}
		}
		//cout << endl;
	}
	
	int maxuse = -1,cnt = 0;
	for( i = 0; i < n; i++ ){
		if( dp[k][i] == 1 ){
			cnt++;
			maxuse = max( maxuse, i );
		}
	}
	
	cout << cnt << endl;
	for( i = 0; i < n; i++ ){
		if( dp[k][i] == 1 ){
			cout << i+1;
			if( i != maxuse )
				cout << " ";
			else
				cout << endl;
		}
	}
	return 0;
}