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