n = input();
d = map(int,raw_input().split())
[x,y] = map(int,raw_input().split())
l = abs(x)+abs(y)

if(not(1<=n<=100000)): print("error")
for a in d:
	if(not(1<=a<=1000000000)): print("error")
if(not(-1000000000<=x<=1000000000)): print("error")
if(not(-1000000000<=y<=1000000000)): print("error")

ans = -1
if l == 0: ans = 0
elif l in d: ans = 1
elif l%2==0:
	if max(d)*2 >= l: ans = 2
else:
	d.sort()
	d1 = [x for x in d if x%2==0]
	d2 = [x for x in d if x%2==1]
	if d1 != []:
		for a in d2:
			low = 0; high = len(d1)-1
			while low < high:
				mid = (high+low) >> 1;
				if(a+d1[mid]>=l): high = mid
				else: low = mid+1
			if(a+d1[low]<l): continue
			b = low
			low = 0; high = len(d1)-1
			while low < high:
				mid = (high+low+1) >> 1;
				if(a>d1[mid] or abs(a-d1[mid])<=l): low = mid
				else: high = mid-1
			if(abs(a-d1[low])>l): continue
			c = low
			if(b<=c): ans = 2
print ans