#include <bits/stdc++.h>
using namespace std;
int cnt;
int ask(string s) {
  cout << s << "\n";
  cout.flush();
  int x;
  cin >> x;
  if (x == 0) {
    exit(0);
  }
  return x;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout.precision(20);
  cout.setf(ios::fixed);
  string sa(300, 'a');
  string sb(300, 'b');
  int cnta = 300 - ask(sa);
  int cntb = 300 - ask(sb);
  int n = cnta + cntb;
  if (cnta == 0) {
    string ans(n, 'b');
    puts(ans.c_str());
    return 0;
  } else if (cntb == 0) {
    string ans(n, 'a');
    puts(ans.c_str());
    return 0;
  }
  int prev = cntb;
  string ans(n, 'a');
  for (int i = 0; i < n; i++) {
    ans[i] = 'b';
    int cur = ask(ans);
    if (cur < prev) {
      prev = cur;
    } else {
      ans[i] = 'a';
    }
  }
  return 0;
}
