#include <iostream>

using namespace std;

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