move = 10 ** 9 / 2 + 10000 
border = move
count_list = {}

100.times do
  puts "? #{border}"
  STDOUT.flush
  res = gets.to_i == 1 ? 1 : -1
  move = [move/2, 1].max
  border += res * move
  count_list[border] ||= 0
  count_list[border] += 1
end

puts count_list.map{|k,v| v}.sort()[0..1].min