N,M,K = map(int,raw_input().split())
E = [[] for i in xrange(N)]
ans = set()
for i in xrange(M):
	a,b,c = map(int,raw_input().split())
	a -= 1; b -= 1
	E[a].append((b,c))
	E[b].append((a,c))
d = map(int,raw_input().split())
def dfs(h,k):
	if k == K:
		ans.add(h)
		return
	for nxt,c in E[h]:
		if c == d[k]:
			dfs(nxt,k+1)
for i in xrange(N):
	dfs(i,0)
print len(ans)
print " ".join(map(lambda x: str(x+1),sorted(ans)))