#include <iostream>
#include <vector>
using namespace std;

int main() {
    int l = 1, r = 1e9, m = (l + r)/2;
    while(true) {
        int res;
        cout << "? "<< m << endl;
        cin >> res;
        if(res) {
            l = m;
        } else {
            r = m - 1;
        }
        if(l == r) break;
        m = (l + r) / 2 + 1;
    }
    cout << "! " << l << endl;
}