l, r = 0, 1000_000_000 + 10
border = (l + r) / 2
puts border
STDOUT.flush

while (res = gets.not_nil!.to_i) != 0
  if res == 1
    l = border - 1
  else
    r = border - 1
  end
  border = (l + r) / 2
  puts "? #{border}"
  STDOUT.flush
end