#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;

//namaega184  

int main(){
	int left=0,right=1000000000,mid=0;
	while(left<right){
		mid=(left+right)/2;
		printf("? %d\n",mid);
		fflush(stdout);
		int res;
		scanf("%d",&res);
		if(res){
			left=mid;
		}
		else{
			right=mid-1;
		}
	}
	printf("! %d\n",mid);
	fflush(stdout);
	
	return 0;
}