#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
Int ask(Int x){
  static Int t = 0;
  cout<<"? "<<max(0LL,x-t)<<endl;
  t++;
  
  Int res;
  cin>>res;
  return res<=0;
}

signed main(){
  Int l=10,r=1e9+100;
  while(l+1<r){
    Int m=(l+r)>>1;
    if(ask(m)) l=m;
    else r=m;
  }
  cout<<"! "<<l<<endl;
  return 0;
}