import sys
sys.setrecursionlimit(100000000)
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())
d.reverse()
now = True
def dfs(h,k):
	global now
	if k == K or now:
		now = True
		return True
	res = False
	for nxt,c in E[h]:
		if c == d[k]:
			res |= dfs(nxt,k+1)
	return res
for i in xrange(N):
	now = False
	if dfs(i,0):
		ans.add(i+1)
print len(ans)
print " ".join(map(str,sorted(ans)))