N,M,K=map(int,raw_input().split())
edge=[[]for i in range(N)]
for i in range(M):
    a,b,c = map(int,raw_input().split())
    edge[a-1].append((b-1,c))
    edge[b-1].append((a-1,c))
d=map(int,raw_input().split())
d.reverse()
ans = []

def dfs(cur,depth):
    if depth==K:
        return True
    for i in range(len(edge[cur])):
        nxt,cost = edge[cur][i]
        if cost == d[depth] and dfs(nxt,depth+1):
            return True
    return False

for i in range(N):
    if dfs(i,0):
        ans.append(i)
print len(ans)
for a in ans:
    print a+1,