#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int a, b, n;
string x;
int main() {
  for (int i = 0; i < 300; i++) x.push_back('a');
  cout << x << '\n';
  cout.flush();
  cin >> a;
  if (a == 0) return 0;
  x = "";
  for (int i = 0; i < 300; i++) x.push_back('b');
  cout << x << '\n';
  cout.flush();
  cin >> b;
  if (b == 0) return 0;
  n = 600 - a - b;
  x = "";
  for (int i = 0; i < n; i++) x.push_back('a');
  if (b == 300) {
    cout << x << '\n';
    cout.flush();
    cin >> b;
    return 0;
  } else if (a == 300) {
    x = "";
    for (int i = 0; i < n; i++) x.push_back('b');
    cout << x << '\n';
    cout.flush();
    cin >> b;
    return 0;
  }
  a -= (300 - n);
  for (int i = 0; i < n; i++) {
    x[i] = 'b';
    cout << x << '\n';
    cout.flush();
    cin >> b;
    if (b == 0) return 0;
    if (b >= a)
      x[i] = 'a';
    else
      a--;
  }
  return 0;
}
