local min, max = 1, 1000000000
io.write("? " .. min .. "\n")
io.flush()
local ret = io.read()
if(ret == "1") then
  io.write("! " .. min .. "\n")
  io.flush()
else
  while(min ~= max) do
    local mid = math.ceil((min + max) / 2)
    io.write("? " .. mid .. "\n")
    io.flush()
    ret = io.read()
    if(ret == "1") then
      max = mid - 1
    else
      min = mid
    end
  end
  io.write("! " .. min .. "\n")
  io.flush()
end