#include <bits/stdc++.h>
using namespace std;
string cr;
void solve(int ok) {
  string t;
  int ind = 0;
  while (ind <= cr.size()) {
    if (ok == 0) break;
    t = cr;
    t.insert(t.begin() + ind, 'b');
    cout << t << "\n";
    cout.flush();
    int ok2;
    cin >> ok2;
    if (ok2 < ok) {
      ok = ok2;
      cr = t;
    }
    ind++;
  }
}
int main() {
  cr.insert(0, 300, 'a');
  cout << cr << "\n";
  cout.flush();
  int ok;
  cin >> ok;
  ok = 300 - ok;
  if (ok == 0) {
    cr = string(300, 'b');
    cout << cr << "\n";
    cout.flush();
    int nrb = 0;
    cin >> nrb;
    nrb = 300 - nrb;
    cr = string(nrb, 'b');
    cout << cr << "\n";
    cout.flush();
    return 0;
  }
  cr = string(ok, 'a');
  cout << cr << "\n";
  cout.flush();
  cin >> ok;
  solve(ok);
  return 0;
}
