package src;

import java.util.*;
public class A{
	static Scanner s = new Scanner(System.in);
	public static void main(String[] args) {
		int n=s.nextInt(),m=s.nextInt(),k=s.nextInt();
		int[] pay = new int[k];
		Way[] way = new Way[m*2];
		ArrayDeque<Integer> deque = new ArrayDeque<>();
		{
			int a,b,c;
			for(int i=0;i<m;i++) {
				a=s.nextInt();
				b=s.nextInt();
				c=s.nextInt();
				if(!deque.contains(a))
					deque.add(a);
				if(!deque.contains(b))
					deque.add(b);
				way[i*2  ]=new Way(a,b,c);
				way[i*2+1]=new Way(b,a,c);
			}
			Arrays.sort(way, (o1, o2) -> o1.a-o2.a);
			for(int i=0;i<k;i++)
				pay[i]=s.nextInt();
			/*
			System.out.println(deque.toString());
			System.out.println(Arrays.toString(pay));
			*/
		}
		for(final int p:pay) {
			int size=deque.size(),poll;
			for(int i=0;i<size;i++) {
				poll=deque.poll();
				for(Way w:way) {
					if(w.a==poll&&w.c==p)
						deque.add(w.b);
					if(w.a>poll)
						break;
				}
			}
		}
		System.out.println(deque.size());
		System.out.println(deque.toString().replaceAll("[^,0-9]", "").replaceAll(",", " "));
	}
}
class Way{
	int a,b,c;
	Way(int a,int b,int c) {
		this.a=a;
		this.b=b;
		this.c=c;
	}
}