import Control.Applicative ((<$>))
import System.IO (hFlush, stdout)

main :: IO ()
main = solve 1 1000000001

solve :: Int -> Int -> IO ()
solve l r = do
  if l+1 == r then putStrLn $ "! " ++ show l
    else do
    let m = (l + r) `div` 2
    putStrLn $ "? " ++ show m
    hFlush stdout
    c <- readLn
    if c == 1 then solve m r else solve l m