#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    int st=1, dr, ans;
    cin>>dr;
    while(st <= dr)
    {
        int med=(st+dr)/2, rasp;
        cout<<"? "<<med<<endl;
        cin>>rasp;
        if(rasp == 1)
        {
            ans=med;
            dr=med-1;
        }
        else
            st=med+1;
    }
    cout<<"! "<<ans<<endl;
    return 0;
}