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
	if ask(99)==-1{
		for i:=1; i<100; i++{
			if ask(0)==0{
				fmt.Println("!", i)
				return
			}
		}
	}
	for i := 1; i < 100; i++ {
		mid := (lb + ub) / 2
		ans := ask(mid-i)
		if ans == -1 {
			ub = mid
		}
		if ans == 1 {
			lb = mid
		}
		if ans == 0 {
			fmt.Println("!", mid)
			return
		}
	}
	fmt.Println("!", lb+1)
	return
}