#include <bits/stdc++.h>
using namespace std;
int main() {
  int na, p = 0, t1, t2;
  string s(300, 'a');
  cout << s << endl;
  cin >> na;
  if (na == 0) return 0;
  na = 300 - na;
  s.assign(na, 'a');
  if (na == 0) s = "b";
  cout << s << endl;
  cin >> t1;
  if (t1 == 0) return 0;
  while (1) {
    string s0 = s.substr(0, p) + "b" + s.substr(p);
    cout << s0 << endl;
    cin >> t2;
    if (t2 == 0) break;
    if (t2 < t1) {
      s = s0;
      t1 = t2;
    }
    p++;
  }
  return 0;
}
