#include<bits/stdc++.h>
using namespace std;
using ll=long long;
constexpr int MOD=998244353;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define replr(i,l,r) for(int i=(l);i<(int)(r);i++)

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N;
  cin>>N;
  string Q(N,'a');
  rep(i,N){
    cout<<"? "<<Q<<endl;
    int base;
    cin>>base;
    bool f=1;
    rep(j,24){
      Q[i]+=1;
      cout<<"? "<<Q<<endl;
      int t;
      cin>>t;
      if(t<base){
        Q[i]-=1;
        f=0;
        break;
      }
      if(t>base){
        f=0;
        break;
      }
    }
    if(f)Q[i]+=1;
  }
  cout<<"! "<<Q<<endl;
}