#include <iostream>

using namespace std;


int dr;

int main()
{
    cin >> dr;
    int st = 1;
    while (st <= dr)
    {
        if (st == dr)
        {
            cout << "! " << dr << '\n';
            return 0;
        }
        int mid = (st + dr) >> 1;
        cout << "? " << mid << '\n';
        cout.flush();
        int val;
        cin >> val;
        if (val == 1)
            dr = mid;
        else
            st = mid + 1;
    }
    return 0;
}