#include <iostream>
#include <cstdio>
using namespace std;

const int INF = 1e+9;

int main() {
	setbuf(stdout,NULL);
	int lb = 0, ub = INF, res;
	while(ub - lb > 1){
		int mid = (lb + ub) / 2;
		printf("? %d\n", mid);
		scanf("%d",&res);
		if(res){
			lb = mid;
		}
		else{
			ub = mid;
		}
	}
	printf("! %d\n", lb);
	return 0;
}