an=int(input())
xs=[int(x) for x in input().split()]
dx,dy=[int(x) for x in input().split()]
o=-1
e=-1
for x in xs:
  if x %2==0: e=max(e,x)
  
  else: o=max(o,x)
  
dx=abs(dx)
dy=abs(dy)
s=dx+dy
if (s==0):  print(0)
elif s%2==1:
  if s <= o: print(1)
  
  else:
    print(2 if s<=o+e else -1)
else:

  if s <= e : print(1)
  
  else : print(2 if s <=max(o+o,e+e) else -1)