N = gets.to_i
D = gets.split.map(&:to_i).sort
X, Y = gets.split.map &:to_i
dist = X.abs + Y.abs
if dist == 0
  p 2
elsif D.include?(dist)
  p 1
elsif D.any?{|d|
    a = (dist - d).abs
    b = dist + d
    D.bsearch{|dd|dd == a} || D.bsearch{|dd|dd == b}
  }
  p 2
else
  p -1
end