#include <bits/stdc++.h>
using namespace std;
const int num = 200001;
int main() {
  string str = "";
  int a, b, temp, store;
  for (int i = 0; i < 300; i++) str += 'a';
  cout << str << "\n";
  fflush(stdout);
  cin >> a;
  if (a == 0) return 0;
  a = 300 - a;
  str = "";
  for (int i = 0; i < 300; i++) str += 'b';
  cout << str << "\n";
  fflush(stdout);
  cin >> b;
  if (b == 0) return 0;
  b = 300 - b;
  str = "";
  for (int i = 0; i < a + b; i++) str += 'a';
  temp = b;
  for (int i = 0; i < str.size() - 1; i++) {
    string ini = str;
    if (str[i] == 'a')
      str[i] = 'b';
    else
      str[i] = 'a';
    cout << str << "\n";
    fflush(stdout);
    cin >> store;
    if (store == 0) return 0;
    if ((store - temp) == 1)
      str = ini;
    else
      temp = store;
  }
  for (int i = 0; i < str.size() - 1; i++) {
    if (str[i] == 'a')
      a--;
    else
      b--;
  }
  if (a)
    str[str.size() - 1] = 'a';
  else
    str[str.size() - 1] = 'b';
  cout << str << "\n";
  fflush(stdout);
  cin >> temp;
  return 0;
  return 0;
}
