#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long INF = mod * mod;
const long double eps = 1e-6;
const long double pi = acos(-1.0);
void debug(vector<long long> &v) {
  int n = v.size();
  for (int i = 0; i < n; i++) {
    if (i > 0) cout << " ";
    cout << v[i];
  }
  cout << "\n";
}
long long mod_pow(long long x, long long n) {
  long long ret = 1;
  while (n > 0) {
    if (n % 2) ret = ret * x % mod;
    x = x * x % mod;
    n >>= 1;
  }
  return ret;
}
struct edge {
  int to, id;
};
vector<edge> G[101];
long long alf[101][26];
vector<string> ealf;
void yaru(int n) {
  cout << "? " << 1 << " " << n << endl;
  for (int i = 1; i <= n; i++)
    for (int j = 0; j < 26; j++) alf[i][j] = 0;
  vector<vector<string>> v(n + 1);
  string alfs;
  for (int i = 0; i < n * (n + 1) / 2; i++) {
    string s;
    cin >> s;
    v[s.size()].push_back(s);
    if (s.size() == 1) alfs += s;
  }
  ealf.push_back(alfs);
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j < v[i].size(); j++) {
      for (int k = 0; k < v[i][j].size(); k++) {
        alf[i][v[i][j][k] - 'a']++;
      }
    }
  }
  int alxor = 0;
  for (int i = 0; i < 26; i++)
    if (alf[1][i] % 2) alxor ^= i;
  for (int i = 1; i <= n / 2; i++) {
    for (int j = 0; j < 26; j++) {
      alf[n + 1 - i][j] = alf[n + 1 - i][j] / i * (i + 1);
    }
    vector<int> rest;
    for (int j = 0; j < 26; j++) {
      int dif = alf[n + 1 - i][j] - alf[n - i][j];
      for (int k = 0; k < dif; k++) rest.push_back(j);
    }
    int xs = rest[0] ^ rest[1];
    alxor ^= xs;
    G[i - 1].push_back({n - i, xs});
    G[n - i].push_back({i - 1, xs});
    for (int j = 0; j < 2; j++) {
      int x = rest[j];
      for (int k = 1; k <= n; k++) {
        alf[k][x] -= i;
      }
    }
  }
}
bool used[100];
int ret[100];
void dfs(int v) {
  for (int j = 0; j < G[v].size(); j++) {
    edge &e = G[v][j];
    if (used[e.to]) continue;
    used[e.to] = true;
    ret[e.to] = ret[v] ^ e.id;
    dfs(e.to);
  }
}
void solve() {
  int n;
  cin >> n;
  if (n <= 3) {
    string ans;
    for (int i = 1; i <= n; i++) {
      cout << "? " << i << " " << i << endl;
      char t;
      cin >> t;
      ans.push_back(t);
    }
    cout << "! " << ans << endl;
    return;
  }
  int mid = (n + 1) / 2;
  yaru(mid);
  yaru(mid - 1);
  yaru(n);
  int alf[2][26] = {};
  for (int i = 0; i < 2; i++) {
    for (int j = 0; j < ealf[i].size(); j++) {
      alf[i][ealf[i][j] - 'a']++;
    }
  }
  int m;
  for (int j = 0; j < 26; j++)
    if (alf[0][j] != alf[1][j]) m = j;
  used[mid - 1] = true;
  ret[mid - 1] = m;
  dfs(mid - 1);
  string out;
  out.resize(n);
  for (int i = 0; i < n; i++) {
    out[i] = 'a' + ret[i];
  }
  cout << "! " << out << endl;
}
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  solve();
  char nyaa;
  cin >> nyaa;
  return 0;
}
