#include<bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  string ans = string(N, 'a');
  for (int i = 0; i < N; i++) {
    int pre = -1;
    bool ok = false;
    for (int j = 0; j < 25; j++) {
      ans[i] = 'a' + j;
      cout << "? " << ans << endl;
      int n;
      cin >> n;
      if (n < pre) {
        ans[i] = 'a' + j - 1;
        ok = true;
        break;
      }
      pre = max(pre, n);
    }    
    if (!ok) ans[i] = 'z';
  }
  cout << "! " << ans << endl;
}