#include <bits/stdc++.h>
using namespace std;
int main() {
  string alla = "", allb = "";
  for (int i = 1; i <= 300; i++) alla += 'a';
  for (int i = 1; i <= 300; i++) allb += 'b';
  cout << alla << endl;
  int ca, cb;
  cin >> ca;
  if (ca == 0) return 0;
  cout << allb << endl;
  cin >> cb;
  if (cb == 0) return 0;
  int cnt = 600 - ca - cb;
  int cnta = 300 - ca, cntb = 300 - cb;
  if (cnta == 0) {
    string s = "";
    for (int i = 1; i <= cntb; i++) s += 'b';
    cout << s << endl;
    int x;
    cin >> x;
    return 0;
  } else if (cntb == 0) {
    string s = "";
    for (int i = 1; i <= cnta; i++) s += 'a';
    cout << s << endl;
    int x;
    cin >> x;
    return 0;
  }
  string test = "", ans = "";
  for (int i = 1; i <= cnt; i++) {
    test += 'a';
    ans += 'a';
  }
  for (int i = 0; i < cnt - 1; i++) {
    test[i] = 'b';
    cout << test << endl;
    int x;
    cin >> x;
    if (x > cntb) {
      test[i] = 'a';
    } else {
      cntb--;
    }
  }
  if (cntb > 0) test.back() = 'b';
  cout << test << endl;
  int x;
  cin >> x;
  return 0;
}
