n = gets.to_i
ds = gets.chomp.split.map(&:to_i).sort.reverse
x, y = gets.chomp.split.map(&:to_i)
r = x.abs + y.abs

if ds.any? {|d| d == r}
  p 1
elsif r.even?
  d_max = ds[0]
  if r <= d_max + d_max
    p 2
  else
    p -1
  end
else

  es = ds.select(&:even?).sort.reverse
  os = ds.select(&:odd?).sort.reverse

  if es.size.zero? or os.size.zero?
    p -1
    exit
  end

  e_max = es[0]
  o_max = os[0]

  if es.any? {|d| d - o_max <= r and r <= d + o_max}
    p 2
  elsif os.any? {|d| d - e_max <= r and r <= d + e_max}
    p 2
  else
    p -1
  end
end