N,M,K = map(int,input().split())
G = [[] for i in range(N)]
for _ in range(M):
    a,b,c = map(int,input().split())
    G[a - 1].append([b - 1, c])
    G[b - 1].append([a - 1, c])
    
D = list(map(int,input().split()))

dp = [[False] * N for i in range(K + 1)]
# dp[k][i] = 次に通る道路の指示がk番目で、i番目にいる
for i in range(N):
    dp[0][i] = True
    
for k in range(K):
    for i in range(N):
        if not dp[k][i]:
            continue
        for child, c in G[i]:
            if D[k] != c:
                continue
            dp[k + 1][child] = True
            
ans = []
for i in range(N):
    if dp[-1][i]:
        ans.append(i + 1)
        
print(len(ans))
print(*ans)