#include <bits/stdc++.h>
using namespace std;
int main() {
  string A = "";
  int resa = 0, resb = 0;
  for (int i = 1; i <= 300; i++) A += 'a';
  cout << A << endl;
  cout.flush();
  cin >> resa;
  if (resa == 0) return 0;
  resa = 300 - resa;
  A.clear();
  for (int i = 1; i <= 300; i++) A += 'b';
  cout << A << endl;
  cout.flush();
  cin >> resb;
  if (resb == 0) return 0;
  resb = 300 - resb;
  int len = resa + resb;
  A.clear();
  for (int i = 0; i < len; i++) {
    A += 'a';
  }
  int tmp;
  for (int i = 0; i < len - 1; i++) {
    A[i] = 'b';
    cout << A << endl;
    cout.flush();
    cin >> tmp;
    if (tmp == 0) return 0;
    if (tmp <= resb) {
      resb--;
    } else
      A[i] = 'a';
  }
  if (resb > 0) A[len - 1] = 'b';
  cout << A << endl;
}
