#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <iostream>

using namespace std;

//namaega184  

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