#include <iostream>
using namespace std;

int main(){
  int l=0,r=1000000000;
  for(int i=0;i<100;i++){
    int center=(l+r)/2;
    cout << "? " << center << endl;
    int tmp;
    cin >> tmp;
    if(tmp == 1){
      l = center;
    }
    else{
      r=center;
    }
  }
  cout << "! " << l << endl;
}