n,m,k=map(int,input().split())
l=[list(map(int,input().split())) for i in range(m)]
d=list(map(int,input().split()))
d.reverse()
c=[[] for i in range(n)]
for i in range(m):
  c[l[i][0]-1].append((l[i][1]-1,l[i][2]))
  c[l[i][1]-1].append((l[i][0]-1,l[i][2]))

ans=[]
for i in range(n):
  p=[i]
  for j1 in range(k):
    p2=set()
    for j2 in range(len(p)):
      for j3 in range(len(c[p[j2]])):
        if c[p[j2]][j3][1]==d[j1]:
          p2.add(c[p[j2]][j3][0])
    p=list(p2)
  if len(p)>0:
    ans.append(str(i+1))
print(len(ans))
print(' '.join(ans))