#include <bits/stdc++.h>
using namespace std;
char s[300];
int main() {
  for (int i = 0; i < 300; i++) {
    cout << 'a';
  }
  cout << endl;
  int a;
  cin >> a;
  a = 300 - a;
  int cnt = 0;
  for (int i = 0; i < 300; i++) {
    cout << 'b';
  }
  cout << endl;
  int b;
  cin >> b;
  b = 300 - b;
  for (int i = 0; i < a + b; i++) {
    s[i] = 'a';
  }
  int y = b;
  for (int j = 0; j < a + b - 1; j++) {
    s[j] = 'b';
    for (int i = 0; i < a + b; i++) {
      cout << s[i];
    }
    cout << endl;
    int x;
    cin >> x;
    if (x == 0) exit(0);
    if (x > y - 1) {
      s[j] = 'a';
      cnt++;
    }
    y = x;
  }
  if (cnt == a) s[a + b - 1] = 'b';
  for (int i = 0; i < a + b; i++) {
    cout << s[i];
  }
  cout << endl;
  int x;
  cin >> x;
  exit(0);
}
