#include <bits/stdc++.h>
using namespace std;
inline long long Min(long long x, long long y) {
  if (x < y) return x;
  return y;
}
inline long long Max(long long x, long long y) {
  if (x > y) return x;
  return y;
}
inline void read(long long &x) {
  x = 0;
  long long f = 1;
  char s = getchar();
  while (s < '0' || s > '9') {
    if (s == '-') f = -1;
    s = getchar();
  }
  while (s >= '0' && s <= '9') {
    x = (x << 3) + (x << 1) + (s ^ 48);
    s = getchar();
  }
  x *= f;
}
int main() {
  long long JZM = 300;
  while (JZM--) cout << "a";
  cout << endl;
  long long A;
  cin >> A;
  A = 300 - A;
  JZM = 300;
  while (JZM--) cout << "b";
  cout << endl;
  long long B;
  cin >> B;
  B = 300 - B;
  long long Len = A + B;
  long long Pre = B;
  string Ans = "";
  for (register int i = Len; i > 1; --i) {
    cout << Ans << "b";
    for (register int j = 1; j < i; ++j) cout << "a";
    cout << endl;
    long long Now;
    cin >> Now;
    if (!Now) return 0;
    if (Now > Pre)
      Ans += "a";
    else
      Ans += "b";
    Pre = Min(Pre, Now);
  }
  if (Pre == 0)
    Ans += "a";
  else
    Ans += "b";
  cout << Ans << endl;
  long long PPL;
  cin >> PPL;
  return 0;
}
