move = 10 ** 9 / 2 + 10000 
border = move

100.times do
  puts "? #{border}"
  STDOUT.flush
  res = gets.to_i == 1 ? 1 : -1
  if move == 1 and res == -1 then
    puts "! #{border - 1}"
    break
  end
  move = [move/2, 1].max
  border += res * move
end