import System.IO

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

main :: IO ()
main = do
    solve 0 (10^9)