#include <bits/stdc++.h>
using namespace std;
int main() {
  string aaa = "";
  string bbb = "";
  for (int i = 0; i < 300; i++) {
    aaa += 'a';
    bbb += 'b';
  }
  int s, t;
  cout << aaa << endl;
  cout.flush();
  cin >> s;
  if (s == 0) return 0;
  cout << bbb << endl;
  cout.flush();
  cin >> t;
  if (t == 0) return 0;
  int n = 600 - (s + t);
  int b = s - (300 - n);
  string st = "";
  for (int i = 0; i < n; i++) st += 'a';
  string ans = "";
  int numB = 0;
  for (int i = 0; i < n - 1; i++) {
    st[i] = 'b';
    cout << st << endl;
    st[i] = 'a';
    cout.flush();
    int x;
    cin >> x;
    if (x == 0) return 0;
    if (x == b - 1)
      ans += 'b';
    else
      ans += 'a';
    numB += ans[i] == 'b';
  }
  if (numB < b)
    ans += 'b';
  else
    ans += 'a';
  cout << ans << endl;
  cout.flush();
  int y;
  cin >> y;
  return 0;
}
