#include<bits/stdc++.h>
using namespace std;

int main(){
	cin.tie(0),ios::sync_with_stdio(false);
	int l=0,r=1e9+1;
	while(r-l>1){
		int m=(l+r)/2;
		cout<<"? "s<<m<<endl;
		bool ans; cin>>ans;
		if(ans)l=m;
		else r=m;
	}
	cout<<"! "s<<l<<endl;
}