#include <iostream>
using namespace std;
int s;
int main(){
    long long mn = 1;
    long long mx = 1000000000;
    long long ce = (mn+mx)/2;
    while(mx-mn > 1){
        cout << "? " << ce << endl;
        cin>>s;
        if(s){
            mn = ce+1;
        }else{
            mx = ce;
        }
        ce = (mn+mx)/2;
    }
    cout << "? " << mn << endl;
    cin>>s;if(!s){cout << "! " << mn << endl;return 0;}
    cout << "? " << ce << endl;
    cin>>s;if(s){cout << "! " << mx << endl;return 0;}
    cout << "! " << ce << endl;
    
}