import collections

n, m, k = [int(x) for x in input().split()]
town = [[] for _ in range(n + 1)]
for i in range(m):
    a, b, c = [int(x) for x in input().split()]
    town[a] += [(b, c)]
    town[b] += [(a, c)]
d = [int(x) for x in input().split()]

cand = set()
for i in range(1, len(town)):
    tovisit = collections.deque()
    tovisit.append((i, 0))
    while len(tovisit) >= 1:
        now, cnt = tovisit.popleft()
        if cnt >= len(d):
            cand.add(now)
            continue
        for nex, cost in town[now]:
            if d[cnt] == cost:
                tovisit.append((nex, cnt + 1))
res = list(cand)
res.sort()

print(len(res))
print(*res)