#include <math.h>
#include <string.h>
#include <stdio.h>

#define NMAX	(100)
#define TMAX	(1000)
#define INF		(99999999)

int toll[TMAX+5];
int nowTown[NMAX+3];

typedef struct{
	int loadA[NMAX+5];
	int loadB[NMAX+5];
}TOWN;

TOWN town[NMAX+3];

void saiki(int nowPos, int N, int depth){
	int i;
	
	if(toll[depth] == 0){
		nowTown[nowPos] = 1;
		return;
	}
	
	for(i=1;i<=N;i++){
		if(nowPos == i){continue;}
		if((town[nowPos].loadA[i] == toll[depth]) || (town[nowPos].loadB[i] == toll[depth])){
			saiki( i, N, depth+1);
		}
	}
}

int main(void){
	int i, N, M, K;
	int cnt=0;
	int minTown = INF;
	
	scanf("%d %d %d", &N, &M, &K);
	for(i=0;i<M;i++){
		int a,b,c;
		scanf("%d %d %d", &a, &b, &c);
		if(town[a].loadA[b] == 0){
			town[a].loadA[b] = c;
		}else{
			town[a].loadB[b] = c;
		}
		
		
		if(town[b].loadA[a] == 0){
			town[b].loadA[a] = c;
		}else{
			town[b].loadB[a] = c;
		}
		
	}
	for(i=0;i<K;i++){
		scanf("%d", &toll[i]);
		toll[i+1] = 0;
	}
	
	for(i=1;i<=N;i++){
		saiki(i, N, 0);
	}
	
	for(i=1;i<=N;i++){
		if(nowTown[i] == 1){
			if(i < minTown){
				minTown = i;
			}
			
			cnt++;
		}
	}
	
	printf("%d\n", cnt);
	printf("%d", minTown);
	for(i=minTown+1;i<=N;i++){
		if(nowTown[i] == 1){
			printf(" %d", i);
		}
	}
	printf("\n");
	return 0;
}