#include <bits/stdc++.h>
using namespace std;
template <class T>
using min_queue = priority_queue<T, vector<T>, greater<T>>;
template <class T1, class T2>
ostream &operator<<(ostream &out, const pair<T1, T2> &a) {
  return out << '(' << a.first << ", " << a.second << ')';
}
template <class T1, class T2>
istream &operator>>(istream &in, pair<T1, T2> &a) {
  return in >> a.first >> a.second;
}
template <class T>
int sz(const vector<T> &v) {
  return (int)v.size();
}
template <class T>
ostream &operator<<(ostream &os, vector<T> v) {
  os << "\n[";
  for (T &first : v) os << first << ',';
  return os << "]\n";
}
const int INF = 2147483647;
const long long LLINF = 9223372036854775807LL;
string test;
int n;
vector<vector<string>> query(int l, int r) {
  int nrs = (r - l + 1) * (r - l + 2) / 2;
  vector<string> S(nrs);
  printf("? %d %d\n", l + 1, r + 1);
  fflush(stdout);
  for (auto i = (0); i != (nrs); ++i) cin >> S[i];
  vector<vector<string>> ret(r - l + 2);
  for (string &s : S) sort((s).begin(), (s).end());
  for (const string &s : S) ret[s.size()].push_back(s);
  return ret;
}
vector<int> analyze(const vector<vector<string>> &v) {
  vector<int> w(v.size());
  for (int i = 0; i < v.size(); i++) {
    w[i] = 0;
    for (const string &s : v[i]) {
      for (char c : s) w[i] += (c - 'a');
    }
  }
  return w;
}
void stop(string &ans) {
  printf("! %s\n", ans.c_str());
  fflush(stdout);
}
void run() {
  cin >> n;
  string ans(n, 'X');
  if (n <= 3) {
    for (auto i = (0); i != (n); ++i) {
      auto v = query(i, i);
      ans[i] = v[1][0][0];
    }
  } else {
    int mid = n / 2;
    vector<int> A = analyze(query(0, mid - 1));
    vector<int> B = analyze(query(1, mid - 1));
    int lsum = 0;
    for (int i = 0; i < mid; i++) {
      int cur = A[i + 1] - (i == mid - 1 ? 0 : B[i + 1]);
      ans[i] = 'a' + (cur - lsum);
      lsum = cur;
    }
    cerr << "  " << ans << " " << n << " " << mid << endl;
    vector<int> C = analyze(query(0, n - 1));
    int sub = 0;
    for (int i = mid; i < n; i++) {
      if (n % 2 == 0) sub += ans[mid + mid - i - 1] - 'a';
      int diff = C[n - i] - (n == i - 1 ? 0 : C[n - i - 1]);
      cerr << diff << "/" << sub << " ";
      ans[i] = 'a' + (diff - sub);
      sub = diff;
      if (n % 2 == 1) sub += ans[mid + mid - i - 1] - 'a';
    }
    cerr << endl;
  }
  stop(ans);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cerr << boolalpha;
  (cout << fixed).precision(10);
  run();
  return 0;
}
