#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-8;
const ull mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

int Q(int x){
	cout<<"? "<<x<<endl;
	int t;
	cin>>t;
	return t;
}

void Ans(int x){
	cout<<"! "<<x<<endl;
}

int main(){
	for(int i=0;i<50;i++){
		int t=Q(i+11);
		if(t==0) Ans(i+11);
		if(t==-1) Ans(i+10);
		if(t<1) return 0;
	}
	int l=40,r=inf,i=0;
	while(r-l>1){
		int m=(l+r)/2,t=Q(m-i);
		if(t>=0) l=m;
		else r=m;
		i++;
	}
	cout<<l+50<<endl;
}