#include <bits/stdc++.h>
using namespace std;
int f(string s) {
  cout << s << endl;
  int w;
  cin >> w;
  if (w == 0) exit(0);
  return w;
}
int main(void) {
  int aCnt, bCnt;
  int k;
  k = f(string(300, 'a'));
  aCnt = 300 - k;
  k = f(string(300, 'b'));
  bCnt = 300 - k;
  int n = aCnt + bCnt;
  string s = string(n, 'a');
  int i = 0;
  while (i < n - 1) {
    s[i] = 'b';
    k = f(s);
    if (k < bCnt) {
      bCnt--;
    } else {
      s[i] = 'a';
    }
    i++;
  }
  if (bCnt) {
    s[n - 1] = 'b';
  }
  k = f(s);
}
