#include <iostream>
using namespace std;
int step=1<<30,n,ans,k;
int K(){if(ans<=step)return 0;cout<<"? "<<ans-step<<'\n';cout.flush();cin>>k;return k;}
int main()
{
    cin>>n;ans=n;
    for(;step;step>>=1)ans-=K()*step;
    cout<<"! "<<ans<<'\n';cout.flush();
    return 0;
}