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)