#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){
  cout<<"? "<<x<<endl;
  Int res;
  cin>>res;
  return res;
}
Int ans(Int x){
  cout<<"! "<<x<<endl;
  exit(0);
}

signed main(){
  Int l=10,r=1e9+100;
  for(Int i=0;i<50;i++){
    Int x=ask(10);
    if(x==0) ans(10+i*2);
    if(x==-1) ans(10+i*2-1);
    Int m=(l+r)>>1;
    Int y=ask(m-(i*2+1));
    if(y>=0) l=m;
    else r=m;
    if(l+1==r) ans(l);
  }
  ans(l);
  return 0;
}