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

int main(){
    int l = 1,r = 1000001;
    int prevx = 0,nowx = -1;
    cout << "? 0" << endl;
    while(abs(l-r) > 1){
        int mid = (l + r) / 2;
        nowx = mid + (mid-prevx);
        cout << "? " << nowx << endl;
        int get;
        cin >> get;
        if(get){
            if(nowx >= prevx){
                l = mid;
            }
            else r = mid + 1;
        }
        else{
            if(nowx >= prevx){
                r = mid;
            }
            else l = mid + 1;
        }
        prevx = nowx;
    }
    cout << "! " << l << endl;
    return 0;
}