#include <bits/stdc++.h>
using namespace std;
long long ask(string& second) {
  cout << second << endl;
  long long t;
  cin >> t;
  if (t == 0) {
    exit(0);
  }
  return t;
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n = 300;
  string second;
  for (long long i = 0; i < n; ++i) second += 'a';
  long long ans1 = ask(second);
  for (long long i = 0; i < n; ++i) second[i] = 'b';
  long long ans2 = ask(second);
  n = 2 * n - ans1 - ans2;
  ans1 = ans1 + n - 300;
  long long cntb = ans1;
  second = string();
  for (long long i = 0; i < n; ++i) second += 'a';
  for (long long i = 0; i + 1 < n; ++i) {
    second[i] = 'b';
    ans2 = ask(second);
    if (ans2 > ans1) {
      second[i] = 'a';
    } else {
      ans1 = ans2;
    }
  }
  if (ans1 > 0) second.back() = 'b';
  ask(second);
}
