from bisect import bisect_left,bisect_right
import sys
readline=sys.stdin.readline

N=int(readline())
D=list(map(int,readline().split()))
D.sort()
x,y=map(int,readline().split())
ans=3
if abs(x)+abs(y) in D:
    ans=1
for d in D:
    l,r=-d,d
    for a in (-d,d):
        for xx,yy in ((x,y),(y,x)):
            if l<=xx<=r:
                m=0
                M=max(abs(r-xx),abs(xx-l))
            else:
                m=min(abs(r-xx),abs(xx-l))
                M=max(abs(r-xx),abs(xx-l))
            m=max(m,abs(a-yy))
            M=max(M,abs(a-yy))
            if bisect_right(D,M)-bisect_left(D,m):
                ans=min(ans,2)
if ans==3:
    ans=-1
print(ans)