#include<iostream>
using namespace std;
int main(){
    int ans;
    int min = 0;
    int max = 1000000000;
    int mid;
    while(1){
        if(min >= max-1){
            cout << "! " << min << endl;
            break;
        }
        mid = min + (max-min)/2;
        cout << "? "<< mid << endl;
        cin >> ans;
        if(ans) min = mid;
        else max = mid;
    }
    return 0;
}