package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	solve()
}

func ask(x int) int {
	fmt.Println("?", x)
	var y int
	y = nextInt()
	return y
}

func solve() {
	lb := -1
	ub := 1000000000
	for i := 0; i < 100; i++ {
		mid := (lb + ub) / 2
		ans := ask(mid)
		if ans == -1 {
			ub = mid - 1
		}
		if ans == 1 {
			lb = mid - 1
		}
		if ans == 0 {
			fmt.Println("!", ans+i)
			break
		}
	}
}

var sc = bufio.NewScanner(os.Stdin)

func nextLine() string {
	sc.Scan()
	return sc.Text()
}
func nextInt() int {
	i, _ := strconv.ParseInt(nextLine(), 10, 64)
	return int(i)
}