N,M,K = map(int,input().split())
G = {i:[] for i in range(1,N+1)}
for _ in range(M):
    a,b,c= map(int,input().split())
    G[a].append((b,c))
    G[b].append((a,c))
D = list(map(int,input().split()))
dp = [[0 for _ in range(K+1)] for _ in range(N+1)]
for i in range(1,N+1):
    for k,c in G[i]:
        if c==D[0]:
            dp[i][1] = 1
            break
for j in range(2,K+1):
    for i in range(1,N+1):
        for k,c in G[i]:
            if c==D[j-1] and dp[k][j-1]==1:
                dp[i][j]=1
                break
A = []
for i in range(1,N+1):
    if dp[i][K]==1:
        A.append(i)
print(len(A))
print(*A)