import java.math.*;
import java.util.*;
class Pare{
	int to;
	int cost;
	Pare(int a,int b){
		to=a;
		cost=b;
	}
}
class Main{
	static void dfs(int from,int nowc,int nowk,ArrayList<Pare>[] mati,int[] d,int[][] memo,boolean[] check){
		if(nowk==d.length){
			check[nowc]=true;
			return;
		}
		if(mati[nowc]==null) return;
		for(int i=0;i<mati[nowc].size();i++){
			if(mati[nowc].get(i).cost==d[nowk] && memo[nowc][nowk]==0 && mati[nowc].get(i).to!=from){
				dfs(nowc,mati[nowc].get(i).to,nowk+1,mati,d,memo,check);
				memo[nowc][nowk]=1;
			}
		}
		
	}
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        int k = sc.nextInt();
        ArrayList<Pare>[] miti = new ArrayList[n];
        for(int i=0;i<m;i++){
        	int a = sc.nextInt()-1;
        	int b = sc.nextInt()-1;
        	int c = sc.nextInt();
        	if(miti[a]==null) miti[a]=new ArrayList<Pare>();
        	if(miti[b]==null) miti[b]=new ArrayList<Pare>();
        	miti[a].add(new Pare(b,c));
        	miti[b].add(new Pare(a,c));
        }
        int[] d = new int[k];
        for(int i=0;i<k;i++){
        	d[i]=sc.nextInt();
        }
        int[][] memo = new int[n][k];
        boolean[] check = new boolean[n];
        for(int i=0;i<n;i++){
        	dfs(-1,i,0,miti,d,memo,check);
        }
        int ans=0;
        for(int i=0;i<n;i++){
        	if(check[i]) ans++;
        }
        System.out.println(ans);
        String aa ="";
        for(int i=0;i<n;i++){
        	if(check[i]) aa+=(i+1)+" ";
        }
        System.out.println(aa.trim());
        
        
    }
}