#include <bits/stdc++.h>
using namespace std;
using ll = long long;

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

  ll N;
  cin >> N;

  auto ask = [&](string &s) {
    cout << "? " << s << endl;
    ll x;
    cin >> x;
    return x;
  };

  string S(N, 'a'), ans = "";
  ll c = ask(S);
  for(ll i = 0; i < N; i++) {
    for(char j = 'b'; j < 'z'; j++) {
      S[i] = j;
      ll t = ask(S);
      if(t < c) {
        ans += 'a';
        break;
      }
      if(t > c) {
        ans += j;
        break;
      }
    }
    if(ans.size() != i + 1) { ans += 'z'; }
    S[i] = 'a';
  }

  cout << "! " << ans << "\n";
}