#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <iomanip>
#include <set>
#include <tuple>
#define mkp make_pair
#define mkt make_tuple
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define all(v) v.begin(),v.end()
using namespace std;
typedef long long ll;
const ll MOD=1e9+7;
template<class T> void chmin(T &a,const T &b){if(a>b) a=b;}
template<class T> void chmax(T &a,const T &b){if(a<b) a=b;}

int ask(int x){
  cout<<"?"<<" "<<x<<endl;
  string s;
  cin>>s;
  if(s=="out") return 0;
  else return 1;
}

const int L=1e3;

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  vector<int> pri(L+20,1);
  for(int i=2;i<=L+10;i++){
    if(pri[i]==0) continue;
    for(int j=2;i*j<=L+10;j++) pri[i*j]=0;
  }

  vector<int> prime={0};
  for(int i=1;i<=L+10;i++) if(pri[i]) prime.push_back(i);

  int P=prime.size();
  int ok=0,ng=P-1;
  map<int,int> mp;
  while(abs(ok-ng)>2){
    int mid=(ok+ng)/2;
    if((mp.count(prime[mid])&&mp[prime[mid]])||ask(prime[mid])){
      ok=mid;
      mp[prime[mid]]=1;
    }else{
      mp[prime[mid]]=0;
      if((mp.count(prime[mid+1])&&mp[prime[mid]]==1)||ask(prime[mid+1])){
        ok=mid;
        mp[prime[mid+1]]=1;
      }else{
        ng=mid+1;
        mp[prime[mid+1]]=0;
      }
    }
  }

  vector<int> table;
  for(int i=prime[ok];i<prime[ng];i++){
    if(i!=prime[ok]&&pri[i]){
      if(ask(i)){
        table.clear();
        table.push_back(i);
      }
    }else table.push_back(i);
  }
  ok=0;ng=table.size();
  while(abs(ok-ng)>1){
    int mid=abs(ok+ng)/2;
    if(ask(table[mid])) ok=mid;
    else ng=mid;
  }

  cout<<"!"<<" "<<table[ok]<<endl;

  return 0;
}