class Yukicoder
  def initialize
    a = 1
    b = 10 ** 9

    while a < b
      c = (a+b)/2

      puts "? #{c}"
      result = gets.to_i

      if result > 0
        a = c
      else
        b = c-1
      end
    end

    puts "! #{a}"
  end
end

Yukicoder.new