#include <iostream>

using namespace std;

int main(){
    int right = 1000000001;
    int left = 1;
    for(int i = 0; i < 50; i++){
        int middle = (right+left)/2;
        cout << "? " << middle << endl;
        cout.flush();
        int ans;
        cin >> ans;
        if(ans == 1){
            left = middle;
        }else{
            right = middle;
        }
    }
    cout << "! " << left << endl;
    return 0;
}