#include <iostream>
using namespace std;
int n,a,b;
int main()
{
    cin>>n;
    a=1;
    b=n;
    while(a<=b)
    {
        int m=(a+b)/2,r;
        cout<<"? "<<m<<'\n';
        cout.flush();
        cin>>r;
        if(r==1)
            b=m-1;
        else
            a=m+1;
    }
    cout<<"! "<<a<<'\n';
    return 0;
}