import sys
sys.setrecursionlimit(10**6)

n,m,k=map(int,input().split())

road=[[] for i in range(n+1)]
ans=set()
for i in range(m):
    a,b,c=map(int,input().split())
    road[b].append([c,a])
    road[a].append([c,b])
   
rireki=list(map(int,input().split()))

def  cal(x,now):
    if now == k:
        ans.add(x)
        return
    for i in road[x]:
        if i[0] == rireki[now]:
            cal(i[1],now+1)

for i in road:
    for j in i:
        if j[0] == rireki[0]:
            cal(j[1],1)
            
            
print(len(ans))
print(*sorted(list(ans)))