local function ask(num)
  io.write("? " .. num .. "\n")
  io.flush()
  local ret = io.read("*l")
  return ret == "safe"
end
local function ans(num)
  io.write("! " .. num .. "\n")
  io.flush()
  os.exit()
end

if not ask(1) then
  ans(0)
end

local left = 0
local right = 1000
local bls, brs = bit.lshift, bit.rshift
while 1 < right - left do
  local mid = brs(left + right, 1)
  local mid2 = mid + 1
  if ask(mid) then
    left = mid
  else
    if ask(mid2) then
      left = mid2
    else
      right = mid
    end
  end
end
ans(left)