#include<bits/stdc++.h>
using namespace std;
int main(){
  int l=1,r=1000000001,m,ans;
  while(r-l>1){
    m=(l+r)/2;
    cout<<"? "<<m<<endl;
    cin>>ans;
    if(ans)l=m;
    else r=m;
  }
  cout<<"! "<<l<<endl;
  exit(0);
}