from collections import defaultdict, deque

n, m, k = map(int, input().split())
edge = defaultdict(list)
for _ in range(m):
    a, b, c = map(int, input().split())
    edge[a].append((b, c))
    edge[b].append((a, c))
D = [0] + list(map(int, input().split()))
Que = deque()
for i in range(1, n + 1):
    Que.append((i, 0))
ANS = []
Seen = [[False for _ in range(n + 1)] for _ in range(k + 1)]
while Que:
    cp, cnt = Que.popleft()
    if cnt == k:
        ANS.append(cp)
        continue
    for np, c in edge[cp]:
        if D[cnt + 1] != c:
            continue
        if Seen[cnt + 1][np]:
            continue
        Seen[cnt + 1][np] = True
        Que.append((np, cnt + 1))

ANS.sort()
print(len(ANS))
print(*ANS)