#include <iostream>
using namespace std;
int s;
int main(){
    long long mn = 1;
    long long mx = 1000000001;
    while(mx-mn > 1){
        long long ce = mn+(mx-mn)/2;
        cout << "? " << ce << endl;
        cin>>s;
        if(s){
            mn = ce;//ce ~ mx
        }else{
            mx = ce;//mn+1 ~ ce-1
        }
    }
    cout << "! " << mn << endl;
    return 0;
}