#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000005
#define Inf64 1000000000000000001LL
int query(long long x, bool f  =true){
	cout<<"? "<<x<<endl;
	if(!f)return 0;
	int res;
	cin>>res;
	if(res==-1)assert(false);
	return res;
}
pair<long long,long long> get(int res,long long last,long long cur){
	long long d = (abs(last-cur)) / 2;
	if(res==1){
		if(last < cur){
			return {cur-d, Inf64};
		}
		else{
			return {-Inf64, cur+d};
		}
	}
	else{
		d = (abs(last-cur)-1)/2;
		if(last < cur){
			return {-Inf64, last+d};
		}
		else{
			return {last-d, Inf64};
		}
	}
	
}
int main(){
	
	long long last = -Inf64;
	long long l = 1,r = 1000000;
	while(l!=r){
		if(last==-Inf64){
			query(l, false);
			last = l;
		}
		else{
			long long mid = (l+r)/2;
			long long cur = mid*2 - last;
			if(cur < last)cur--;
			else cur++;
			if(abs(cur) > 1000000000){
				last = -Inf64;
				continue;
			}
			int res = query(cur);
			auto p = get(res, last, cur);
			l = max(l,p.first);
			r = min(r,p.second);
			last = cur;
		}
		
	}
	cout<<"! "<<l<<endl;
	return 0;
}