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

int ask(int Y){
    cout<<"? "<<Y<<endl;
    int res;
    cin>>res;
    return res;
}

int main(){
    int x=ask(80);

    if(x>=0){
        for(int i=1;i<100;i++){
            x=ask(0);
            if(x==0){
                cout<<"! "<<i<<endl;
                return 0;
            }
        }
    }
    int cnt=1;
    int lb=80,ub=1e9;

    while(ub-lb>1){
        int mid=(ub+lb)/2;
        x=ask(mid-cnt);


        if(x>=0){
            ub=mid;
        }
        else lb=mid;
        cnt++;
    }
    cout<<"! "<<lb<<endl;
    return 0;
}