#include <bits/stdc++.h>
using namespace std;
using ld = long double;
using ll = long long;
using vi = vector<int>;
using pii = pair<int, int>;
const int MX = 1e5;
int query(const string& t) {
  cout << t << '\n';
  cout.flush();
  int d;
  cin >> d;
  if (d == 0) exit(0);
  return d;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string t = "a";
  int q_a = query(t);
  t = string(q_a, 'b');
  int cant_a = query(t);
  int n = q_a + 1;
  int cant_b = n - cant_a;
  t = string(n, 'a');
  if (cant_a == n) query(t);
  string res = "";
  int usado_b = 0;
  for (int i = 0; i < n - 1; ++i) {
    t[i] = 'b';
    if (query(t) < cant_b) {
      res += "b";
      usado_b++;
    } else {
      res += "a";
    }
    t[i] = 'a';
  }
  if (cant_b > usado_b)
    res += "b";
  else
    res += "a";
  query(res);
  return 0;
}
