from queue import Queue

used = set()
n, m, k = map(int, input().split())
node = [[] for i in range(n)]
for i in range(m):
    a, b, c = map(int, input().split())
    node[a-1].append((b-1, c))
    node[b-1].append((a-1, c))
d = list(map(int, input().split()))
qu = Queue()
for i in range(n):
    qu.put((i, 0))
res = []
while not qu.empty():
    (p, t) = qu.get()
    if (p, t) in used: continue
    used.add((p, t))
    if t == k:
        res.append(p)
        continue
    for (np, c) in node[p]:
        if d[t] != c: continue
        qu.put((np, t+1))
res.sort()
print(len(res))
ans = ""
for i in res:
    ans += str(i+1)+" "
print(ans.strip())