class Peek:
    def __init__(self, i, A):
        self.i = i
        self.A = A
        self.V = []
        self.B = False
    def __str__(self):
        return str(self.i) + ":" + str(self.A) + "," + str(self.B) + "," + str(self.V)
        
N, M = map(int, input().split())

A = []
for i, a in enumerate(list(map(int, input().split()))):
    A.append(Peek(i, a))
    
for _ in range(M):
    u, v = map(int, input().split())
    A[u-1].V.append(v-1)
    A[v-1].V.append(u-1)
    
K = int(input())
for b in list(map(int, input().split())):
    A[b-1].B = True

S = []
for P in A:
    noInput = True
    for i in P.V:
        if P.A > A[i].A:
            noInput = False
        elif P.A == A[i].A:
            P.V.remove(i)
    if noInput:
        S.append(P)
        
op = []
while len(S) > 0:
    n = S.pop(0)
    b = n.B
    if b:
        n.B = False
        op.append(n.i + 1)
    for i in n.V:
        m = A[i]
        m.V.remove(n.i)
        if b:
            m.B =  not m.B
        noInput = True
        for i in m.V:
            if m.A > A[i].A:
                noInput = False
            elif m.A == A[i].A:
                m.V.remove(i)
        if noInput:
            S.append(m)
            
if any([i.B for i in A]):
    print(-1)
else:
    print(len(op))
    for p in op:
        print(p)