from collections import defaultdict, deque
from typing import Deque


def main():
    N, M, K = map(int, input().split())
    routes = [list(map(int, input().split())) for _ in range(M)]
    routes_cost_dict = defaultdict(lambda: defaultdict(set))
    for route in routes:
        routes_cost_dict[route[2]][route[0]].add(route[1])
        routes_cost_dict[route[2]][route[1]].add(route[0])
    history = list(map(int, input().split()))

    dp_table = [[False for _ in range(N)] for _ in range(K+1)]
    dp_table[0] = [True for _ in range(N)]

    for ctr, cost in enumerate(history, 1):
        for city_idx in range(1, N+1):
            for dest_city_idx in routes_cost_dict[cost][city_idx]:
                dp_table[ctr][dest_city_idx-1] |= dp_table[ctr-1][city_idx-1]

    last_city_candidates = set(
        filter(lambda city_idx: dp_table[K][city_idx], range(N)))
    print(len(last_city_candidates))
    print(*map(lambda num: num+1, sorted(last_city_candidates)))


if __name__ == "__main__":
    main()