package main

import "fmt"

func main() {
	solve()
}

func ask(x int) int {
	fmt.Println("?", x)
	var y int
	fmt.Scan(&y)
	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("!", mid+i)
			break
		}
	}
}