#include <bits/stdc++.h>
using namespace std;
int ask(string foo) {
  cout << foo << endl;
  fflush(stdout);
  int t;
  cin >> t;
  if (t == 0) exit(0);
  return t;
}
int main() {
  int n1 = 300 - ask(string(300, 'a'));
  int n2 = 300 - ask(string(300, 'b'));
  int n = n1 + n2;
  if (n1 == n) {
    ask(string(n, 'a'));
  }
  if (n2 == n) {
    ask(string(n, 'b'));
  }
  string s(n, 'a');
  int now = n2;
  for (int i = 0; i < n; i++) {
    s[i] = 'b';
    int cur = ask(s);
    if (cur > now) {
      s[i] = 'a';
    } else {
      now = cur;
    }
  }
  return 0;
}
