package main

import (
	"fmt"
)

func main() {
	solve()
}

func ask(x int)int{
	fmt.Println("?", x)
	var ans int
	fmt.Scan(&ans)
	return ans
}

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