#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;}

map<int,int> mp;

int ask(int x){
  if(mp.count(x)) return mp[x];

  cout<<"?"<<" "<<x<<endl;
  string s;
  cin>>s;
  if(s=="out") return mp[x]=0;
  else return mp[x]=1;
}

const int L=1e3;

int main(){
  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;
  while(abs(ok-ng)>2){
    int mid=(ok+ng)/2;
    if(ask(prime[mid])) ok=mid;
    else{
      if(ask(prime[mid+1])) ok=mid+1;
      else ng=mid+1;
    }
  }

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

  cout<<"!"<<" "<<ans<<endl;

  return 0;
}