#include <bits/stdc++.h>
using namespace std;
long long n = 300, x, a, b, res;
string s;
long long query(string s) {
  printf("%s\n", s.c_str()), fflush(stdout);
  scanf("%lld", &x);
  if (!x) exit(0);
  return x;
}
signed main() {
  a = n - query(string(n, 'a')), b = n - query(string(n, 'b'));
  n = a + b, s = string(n, 'a'), res = b;
  for (long long i = 0; i < n; i++) {
    if (i == n - 1)
      s[i] = (res ? 'b' : 'a');
    else
      s[i] = 'b';
    if ((x = query(s)) < res)
      res = x;
    else
      s[i] = 'a';
  }
  return 0;
}
