N=int(input())
D=sorted(map(int,input().split()))
x,y=map(int,input().split())

ODD=0
EVEN=0

for d in D:
    if d%2==0:
        EVEN=d
    else:
        ODD=d

if x==0 and y==0:
    print(0)
    exit()

Distance=abs(x)+abs(y)

if Distance in D:
    print(1)
    exit()

S=set(D)
for d in D:
    x=Distance-d

    if x>=0:
        if (x%2==ODD%2 and x<=ODD) or (x%2==EVEN%2 and x<=EVEN):
            print(2)
            exit()
    else:
        if -x in S:
            print(2)
            exit()

print(-1)