#include <iostream>
using namespace std;

int main(){
   int max = 1e9,min = 1;
   bool f;
   for(int i = 0;i < 100;i++){
      cout << "? " << (max + min) / 2 << endl;
      cin >> f;
      f ? min = (max + min) / 2 : max = (max + min) / 2;
      if(max - min == 1){
         cout << "! " << min << endl;
         return 0;
      }
   }
}