#include <bits/stdc++.h>
using namespace std;
const bool MULTI_TEST = false;
const long long INF = 1e18;
void change(string &s, long long pos) { s[pos] = (s[pos] == 'a' ? 'b' : 'a'); }
long long ask(string &s) {
  long long ans;
  cout << s << endl;
  cin >> ans;
  return ans;
}
void solve2(long long n, long long cnta, long long cntb) {
  string s, s2;
  for (long long i = 0; i < n; i++) {
    s += 'a';
    s2 += 'b';
  }
  if (cnta == 0) {
    cout << s2 << endl;
    return;
  }
  if (cntb == 0) {
    cout << s << endl;
    return;
  }
  long long res = cntb;
  for (long long i = 0; i < n - 1; i++) {
    change(s, i);
    long long res2 = ask(s);
    if (res2 > res) {
      change(s, i);
    } else {
      res = res2;
    }
    if (res == 0) {
      return;
    }
  }
  if (res > 0) {
    change(s, n - 1);
  }
  ask(s);
}
void solve() {
  long long MAXN = 300;
  string st1, st2;
  for (long long i = 0; i < MAXN; i++) {
    st1 += 'a';
    st2 += 'b';
  }
  long long cnta = 300 - ask(st1);
  long long cntb = 300 - ask(st2);
  long long n = cnta + cntb;
  solve2(n, cnta, cntb);
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  if (MULTI_TEST) {
    cin >> t;
  }
  for (long long i = 0; i < t; i++) {
    solve();
  }
  return 0;
}
