#include<sstream>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<numeric>
#include<functional>
#include<algorithm>
#include<bitset>
using namespace std;
#define INF (1<<29)
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define uniq(v) v.erase(unique(all(v)),v.end())
#define indexOf(v,x) (find(all(v),x)-v.begin())



int solve1(){
	int t=0,res;
	while(1){
		cout<<"? "<<0<<endl;
		cin>>res;
		if(res==0)return t;
		t++;
	}
}
int solve2(){
	int lb=50,ub=1000000000+1,t=0;
	while(1){
		int mid=(lb+ub)/2;
		cout<<"? "<<mid<<endl;
		int res;
		cin>>res;
		if(res==-1){
			ub=mid;
		}else if(res==0){
			return max(0,mid+t);
		}else{
			lb=mid+1;
		}
		t++;
		lb--;
		ub--;
	}
}

int main(){
	int res;
	cout<<"? 50"<<endl;
	cin>>res;

	if(res==0)cout<<"! "<<50<<endl;
	else if(res==-1)cout<<"! "<<solve1()+1<<endl;
	else cout<<"! "<<solve2()+1<<endl;


	return 0;
}