#include <bits/stdc++.h>
using namespace std;
template <class c>
struct rge {
  c b, e;
};
template <class c>
rge<c> range(c i, c j) {
  return rge<c>{i, j};
}
template <class c>
auto dud(c* x) -> decltype(cerr << *x, 0);
template <class c>
char dud(...);
struct debug {
  template <class c>
  debug& operator<<(const c&) {
    return *this;
  }
};
vector<char*> tokenizer(const char* args) {
  char* token = new char[111];
  strcpy(token, args);
  token = strtok(token, ", ");
  vector<char*> v({token});
  while (token = strtok(NULL, ", ")) v.push_back(token);
  return reverse(v.begin(), v.end()), v;
}
void debugg(vector<char*> args) { cerr << "\b\b "; }
template <typename Head, typename... Tail>
void debugg(vector<char*> args, Head H, Tail... T) {
  debug() << " [" << args.back() << ": " << H << "] ";
  args.pop_back();
  debugg(args, T...);
}
long long mod = 1e9 + 7;
const int MX = 0x3f3f3f3f;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string t, st1, st2;
  int edis, i, a, b;
  for (i = 1; i <= 300; i++) st1 += 'a';
  for (i = 1; i <= 300; i++) st2 += 'b';
  cout << st1 << endl;
  cin >> a;
  if (!a) return 0;
  a = 300 - a;
  cout << st2 << endl;
  cin >> b;
  if (!b) return 0;
  b = 300 - b;
  if (a == 0) {
    for (i = 1; i <= b; i++) cout << 'b';
    return 0;
  } else if (b == 0) {
    for (i = 1; i <= a; i++) cout << 'a';
    return 0;
  }
  edis = b;
  for (i = 1; i <= a + b; i++) t += 'a';
  i = 0;
  a = a + b - 1;
  while (i < a) {
    t[i] = 'b';
    cout << t << endl;
    cin >> b;
    if (b == edis - 1) {
      edis = b;
      if (!edis) return 0;
    } else {
      t[i] = 'a';
    }
    i++;
  }
  t[a] = 'b';
  cout << t << endl;
  cin >> edis;
  return 0;
}
