#include <iostream>

using namespace std;

int query(int x)
{
    cout<<"? "<<x<<endl;
    int res;
    cin>>res;
    return res;
}

int main()
{
    int n,l,r,mid,pos;
    cin>>n;
    l=1;
    r=n;
    while(l<=r)
    {
        mid=(l+r)/2;
        if(query(mid)==1)
        {
            r=mid-1;
        }
        else{
            pos=mid;
            l=mid+1;
        }    
}
    cout<<"! "<<l<<endl;
    return 0;
}