#include <bits/stdc++.h>
using namespace std;
long long n, x, k, z, m, pos, q, ans_v, y;
long long x1, p1, x2;
long long b[200500], c[200500];
pair<long long, long long> a[200500];
vector<long long> f;
vector<long long> g[200500];
string s;
long long ask(string s) {
  cout << s << endl;
  fflush(stdout);
  long long x;
  cin >> x;
  if (x == 0) {
    exit(0);
  }
  return x;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  long long numa, numb;
  for (int i = 0; i < 300; i++) {
    cout << "a";
  }
  cout << endl;
  fflush(stdout);
  cin >> numa;
  if (numa == 0) {
    return 0;
  }
  numa = 300 - numa;
  for (int i = 0; i < 300; i++) {
    cout << "b";
  }
  cout << endl;
  fflush(stdout);
  cin >> numb;
  if (numb == 0) {
    return 0;
  }
  numb = 300 - numb;
  long long n = numa + numb;
  string pat;
  for (int i = 0; i < n; i++) {
    s.push_back('a');
    pat.push_back('a');
  }
  long long cur_ans = n - numa;
  for (int i = 0; i < n - 1; i++) {
    pat[i] = 'b';
    long long x = ask(pat);
    if (x < cur_ans) {
      s[i] = 'b';
    }
    cur_ans = x;
  }
  if (n - numb < cur_ans) {
    s[n - 1] = 'b';
  }
  long long x = ask(s);
  return 0;
}
