#include <bits/stdc++.h>
using namespace std;
int query(string s) {
  cout << s << "\n";
  cout.flush();
  int a;
  cin >> a;
  return a;
}
int ans(string s) {
  cout << s << "\n";
  cout.flush();
  int a;
  cin >> a;
  return 0;
}
int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  string a(300, 'a');
  string b(300, 'b');
  int qa = query(a);
  int qb = query(b);
  int n = 300 * 2 - (qa + qb);
  int na = qb - (300 - n), nb = qa - (300 - n);
  if (!na) return ans(string(n, 'b'));
  if (!nb) return ans(string(n, 'a'));
  string u = string(n, 'a');
  int curr = nb;
  for (int i = 0; i < n; i++) {
    u[i] = 'b';
    int p = query(u);
    if (p < curr)
      curr = p;
    else
      u[i] = 'a';
    if (p == 0) return 0;
  }
  return 0;
}
