from collections import deque
N,M = map(int,input().split())
A = [0]+list(map(int,input().split()))
G = {i:[] for i in range(1,N+1)}
indeg = [0]*(N+1)
for _ in range(M):
    u,v = map(int,input().split())
    if A[u]>A[v]:
        G[v].append(u)
        indeg[u] += 1
    if A[u]<A[v]:
        G[u].append(v)
        indeg[v] += 1
K = int(input())
B = list(map(int,input().split()))
L = [0]*(N+1)
for i in range(K):
    L[B[i]] = 1
que = deque([])
for i in range(1,N+1):
    if indeg[i]==0:
        que.append(i)
ans = []
while que:
    x = que.popleft()
    if L[x]==1:
        flag = 1
    else:
        flag = 0
    if flag==1:
        ans.append(x)
        L[x] = 0
    for y in G[x]:
        indeg[y] -= 1
        if flag==1:
            L[y] = 1-L[y]
        if indeg[y]==0:
            que.append(y)
if sum(L)==0:
    print(len(ans))
    for a in ans:
        print(a)
else:
    print(-1)