from bisect import bisect,bisect_left

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

ODD=[]
EVEN=[]

for d in D:
    if d%2==0:
        EVEN.append(d)
    else:
        ODD.append(d)

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

Distance=abs(x)+abs(y)

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

for d in D:
    if d<=Distance:
        L,R=Distance-d,Distance+d

    else:
        L,R=d-Distance,Distance+d

    if L%2==0:
        x0=bisect(EVEN,L-1)
        x1=bisect(EVEN,R)
    else:
        x0=bisect(ODD,L-1)
        x1=bisect(ODD,R)

    if x0!=x1:    
        print(2)
        exit()

print(-1)