import sys
input=lambda: sys.stdin.readline().rstrip()
n,m,k=map(int,input().split())
edge = [[] for i in range(n)]
for i in range(m):
  a,b,c=map(int,input().split())
  edge[a-1].append([c,b-1])
  edge[b-1].append([c,a-1])
D=[int(i) for i in input().split()][::-1]
Ans=[]
for i in range(n):
  S=[i]
  for j in range(k):
    SS=set()
    for s in S:
      for c,g in edge[s]:
        if c==D[j]:
          SS.add(g)
    S=list(SS)
    if not S:
      break
    else:
      continue
  else:
    Ans.append(i+1)
print(len(Ans))
print(*Ans)