#include <iostream>

using namespace std;

int main()
{
   int n; cin >> n;
   int left = 1, right = n;
   while ( left <= right ) {
      int mid = left + ( right - left ) / 2;

      cout << "? " << mid; cout.flush ();
      bool answer; cin >> answer;

      if ( answer == 1 )
        right = mid - 1;
      else
        left = mid + 1;
   }
   cout << "! " << left;
    return 0;
}