import sys
sys.setrecursionlimit(1000000)
N,M,K = map(int,input().split())
graph = [[] for i in range(N)]
for i in range(M):
	a,b,c = map(int,input().split())
	graph[a-1].append((b-1,c))
	graph[b-1].append((a-1,c))
d = [int(i) for i in input().split()]
used = [[False for j in range(K)]for i in range(N)]
ans = set([])
def dfs(n,c):
	if c == K:
		ans.add(n+1)
		return
	if used[n][c]:
		return
	used[n][c] = True
	for e in graph[n]:
		if e[1] == d[c]:
			dfs(e[0],c+1)
for i in range(N):
	dfs(i,0)
print(len(ans))
print(' '.join(str(i) for i in sorted(list(ans))))