import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class Main92 {
	public static void main(String[] args) {
		Main92 p = new Main92();
	}

	public Main92() {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		int k = sc.nextInt();
		d = new int[k];
		ArrayList<ArrayList<Edge>> city = new ArrayList<ArrayList<Edge>>();
		for(int i=0;i<n;i++){
			city.add(new ArrayList<Edge>());
		}
		
		for(int i=0;i<m;i++){
			int a = sc.nextInt()-1;
			int b = sc.nextInt()-1;
			int c = sc.nextInt();
			city.get(a).add(new Edge(b, c));
			city.get(b).add(new Edge(a, c));
		}
		for(int i=0;i<k;i++)
			d[i] = sc.nextInt();
		solve(n,m,k,city);
	}
	
	private boolean[] isOk;
	private int[] d;
	private int[][] memo;
	public void solve(int n, int m, int k, ArrayList<ArrayList<Edge>> city) {
		isOk = new boolean[city.size()];
		memo = new int[n][k];
		
		for(int i=0;i<n;i++)
			dfs(i, 0, city);
		int c = 0;
		for(int i=0;i<isOk.length;i++)
			if(isOk[i])
				c++;
	
		System.out.println(c);
		for(int i=0;i<isOk.length;i++){
			if(isOk[i]){
				c--;
				System.out.print((i+1) + "" + (c>0 ? ' ' : '\n'));
			}
		}
	}

	private void dfs(int curc, int curk, ArrayList<ArrayList<Edge>> city) {
			
//		System.out.println(curc+" "+curk);
		if(curk==d.length){
			isOk[curc] = true;
			return;
		}
		if(memo[curc][curk]==1)
			return;
		
		
		for(int i=0;i<city.get(curc).size();i++){
			if(city.get(curc).get(i).c==d[curk])
				dfs(city.get(curc).get(i).b, curk+1, city);
			memo[curc][curk] = 1;
		}
		
	}
	
	private class Edge{
		int b;
		int c;
		public Edge(int b, int c) {
			
			this.b = b;
			this.c = c;
		}
		
		
	}

}