from collections import defaultdict
N, M, K = map(int, input().split())
G = [defaultdict(list) for _ in range(N + 1)]
for i in range(M):
    u, v, w = map(int, input().split())
    G[u][w].append(v)
    G[v][w].append(u)

# G[src][cost] = [nex, ...]

D = list(map(int, input().split()))
D.reverse()

ans = []
for i in range(1, N + 1):
    # 今頂点iにいるとする
    cur = {i}
    for d in D:
        nexset = set()
        # このターンはコストd掛かってる
        for pos in cur:
            # G[pos][d]
            for nex in G[pos][d]:
                nexset.add(nex)        
        if nexset:
            cur = nexset
        else:
            break
    else:
        ans.append(i)
print(len(ans))
print(*ans)