#include <bits/stdc++.h>
using namespace std;
const int MAXN = 300;
string s, ans;
int numA, numB;
int num = 0;
int getRes() {
  cout << s << endl;
  int x;
  cin >> x;
  if (x == 0) {
    exit(0);
  }
  return x;
}
int main() {
  for (int i = 0; i < 300; i++) {
    s.append(1, 'a');
  }
  numA = 300 - getRes();
  s = "";
  for (int i = 0; i < 300; i++) {
    s.append(1, 'b');
  }
  numB = 300 - getRes();
  if (numA == 0) {
    s = "";
    for (int i = 0; i < numB; i++) {
      s.append(1, 'b');
    }
    getRes();
  } else if (numB == 0) {
    s = "";
    for (int i = 0; i < numA; i++) {
      s.append(1, 'a');
    }
    getRes();
  }
  s = "";
  for (int i = 0; i < numA + numB; i++) {
    s.append(1, 'a');
  }
  int expect = numB;
  for (int i = 0; i < numA + numB; i++) {
    s[i] = 'b';
    int current = getRes();
    if (current < expect) {
      expect--;
    } else {
      s[i] = 'a';
    }
  }
  return 0;
}
