n = gets.to_i
d = gets.split.map(&:to_i)
x, y = gets.split.map(&:to_i)
sum = x.abs + y.abs
if x == 0 && y == 0
    p 0
elsif d.include?(sum)
    p 1
else
    if sum % 2 == 0
        if d.max * 2 >= sum
            p 2
        else
            p -1
        end
    else
        hoge = d.select{|x| x % 2 == 0}
        foo = d.select{|x| x % 2 == 1}
        if hoge.empty? || foo.empty?
            p -1
        elsif hoge.max + foo.max >= sum
            p 2
        else
            p -1
        end
    end
end