n, m, k = [ int(v) for v in input().split() ]
tool_list = [[] for i in range(n)]

for i in range(m):
    connect = [ int(v) for v in input().split() ]
    tool_list[connect[0]-1].append([connect[1]-1,connect[2]])
    tool_list[connect[1]-1].append([connect[0]-1,connect[2]])


suspect = [i for i in range(n)]
payment = [ int(v) for v in input().split() ]

for i in payment:
    new_suspect = []
    for j in suspect:

        for k in tool_list[j]:

            if k[1] == i:
                new_suspect.append(k[0])
    suspect = new_suspect


print(len(suspect))
print(" ".join([str(i+1) for i in sorted(suspect)]))