n,m=map(int,input().split())
a=list(map(int,input().split()))
l=[list(map(int,input().split())) for i in range(m)]
k=int(input())
b=list(map(int,input().split()))

connection=[[] for i in range(n)]
for i in range(m):
  if a[l[i][0]-1]<a[l[i][1]-1]:
    connection[l[i][0]-1].append(l[i][1]-1)
  if a[l[i][1]-1]<a[l[i][0]-1]:
    connection[l[i][1]-1].append(l[i][0]-1)

L=[0]*n
for i in range(k):
  L[b[i]-1]=1

for i in range(n):
  a[i]=(a[i],i)
a.sort(key=lambda x:x[0])

ct=0
ans=[]
for i in range(n):
  x=a[i][1]
  if L[x]==1:
    L[x]=0
    ct+=1
    ans.append(x)
    for j in connection[x]:
      L[j]=1-L[j]

if sum(L)!=0:
  print(-1)
  exit()

print(ct)
for i in range(ct):
  print(ans[i]+1)