#include<bits/stdc++.h>
using namespace std;
int main(){
  int l=0,r=1<<20;
  cout<<"? "<<l<<endl;
  int say=r,las=l;
  while(r-l>1){
    cout<<"? "<<say<<endl;
    int ret;
    cin>>ret;
    int m=(l+r)/2;
    if(las<say){
      if(ret){
        l=m;
        las=say;
        m=(l+r)/2;
        say=2*m-say;
      }
      else{
        r=m;
        las=say;
        m=(l+r)/2;
        say=2*m-las;
      }
    }
    else{
      if(ret){
        r=m+1;
        las=say;
        m=(l+r)/2;
        say=2*m-say;
      }
      else{
        l=m+1;
        las=say;
        m=(l+r)/2;
        say=2*m-las;
      }
    }
    //cerr<<l<<" "<<r<<endl;
  }
  cout<<"! "<<l<<endl;
}