#include <bits/stdc++.h>
#define REP(i,n,N) for(int i=(n);i<(int) N;i++)
#define p(s) cout<<(s)<<endl
typedef long long ll;
using namespace std;
const ll inf=1e9;


int main(){
	ll a;
	ll lb=0,ub=inf;
	REP(i,1,100){
		ll mid=(lb+ub)/2;
		cout<<"? "<<mid<<endl;
		cin>>a;
		if(a) lb=mid;
		else ub=mid;
	}
	cout<<"! "<<lb<<endl;
	return 0;
}