#include <bits/stdc++.h>
using namespace std;
signed main() {
  int a, b, n = 300;
  for (int i = 0; i < n; i++) {
    cout << 'a';
  }
  cout << "\n";
  cout.flush();
  cin >> a;
  if (a == 0) exit(0);
  for (int i = 0; i < n; i++) {
    cout << 'b';
  }
  cout << "\n";
  cout.flush();
  cin >> b;
  if (b == 0) exit(0);
  a = n - a;
  b = n - b;
  n = a + b;
  vector<int> used(n, 0);
  string s;
  for (int i = 0; i < n; i++) {
    s += 'a';
  }
  int v;
  for (int i = 0; i < n - 1; i++) {
    s[i] = 'b';
    cout << s << "\n";
    cout.flush();
    cin >> v;
    if (v == 0) exit(0);
    if (v < b) used[i] = 1;
    s[i] = 'a';
  }
  int am = 0;
  for (int i = 0; i < n; i++) {
    if (used[i]) {
      am++;
      s[i] = 'b';
    }
  }
  if (am < b) {
    used[n - 1] = 1;
    s[n - 1] = 'b';
  }
  cout << s << "\n";
  cout.flush();
  return 0;
}
