import sys
from collections import deque

input = sys.stdin.buffer.readline

n, m = map(int, input().split())
A = list(map(int, input().split()))
graph = [[] for _ in range(n)]
deg = [0] * n
for _ in range(m):
    a, b = map(int, input().split())
    a, b = a - 1, b - 1
    if A[b] > A[a]:
        graph[a].append(b)
        deg[b] += 1
    if A[a] > A[b]:
        graph[b].append(a)
        deg[a] += 1
k = int(input())
B = list(map(int, input().split()))


finished = [0] * n
lamp = [0] * n
for b in B:
    lamp[b - 1] = 1

start = deque()

for i in range(n):
    if deg[i] == 0:
        start.append(i)

ans = []

while start:
    v = start.popleft()
    if lamp[v] == 0:
        finished[v] = 1
        for u in graph[v]:
            if finished[u]:
                continue
            start.append(u)
    else:
        ans.append(v + 1)
        outflag = 0
        lamp[v] = 0
        finished[v] = 1
        for u in graph[v]:
            lamp[u] ^= 1
            if not finished[u]:
                start.append(u)

if sum(lamp) > 0:
    print(-1)
    exit()

print(len(ans))
for a in ans:
    print(a)