import sys
import io, os
input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline

n, m = map(int, input().split())
A = list(map(int, input().split()))
g = [[] for i in range(n)]
for i in range(m):
    u, v = map(int, input().split())
    u, v = u-1, v-1
    if A[u] < A[v]:
        g[u].append(v)
    elif A[u] > A[v]:
        g[v].append(u)
k = int(input())
B = list(map(int, input().split()))
B = [b-1 for b in B]
C = [0]*n
for b in B:
    C[b] = 1

q = []
import heapq
for b in B:
    q.append((A[b], b))
heapq.heapify(q)
ans = []
while q:
    a, v =heapq.heappop(q)
    if C[v] == 0:
        continue
    C[v] = 0
    ans.append(v+1)
    for u in g[v]:
        C[u] = 1-C[u]
        heapq.heappush(q, (A[u], u))
if sum(C) > 0:
    print(-1)
    exit()
print(len(ans))
print(*ans, sep='\n')