#include <iostream>
using namespace std;
int n,x;
int main()
{
    cin>>n;
    int st=1,dr=n,mid,sol=n;
    while (st<=dr)
    {
        mid=(st+dr)/2;
        cout<<'?'<<' '<<mid;
        cout.flush();
        cin>>x;
        if (x==1)
        {
            sol=mid;
            dr=mid-1;
        }
        else
            st=mid+1;
    }
    cout<<'!'<<' '<<sol;
}