#include <bits/stdc++.h>
using namespace std;
const long long INF = (long long)1e18;
const int mod = (int)1e9 + 7;
const int MAXN = (int)3e5 + 5;
long long n;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  string a, b;
  for (int i = 0; i < 300; i++) {
    a += 'a';
    b += 'b';
  }
  int q1, q2;
  cout << a << endl << flush;
  cin >> q1;
  if (q1 == 0) return 0;
  cout << b << endl << flush;
  cin >> q2;
  if (q2 == 0) return 0;
  int numA = 300 - q1, numB = 300 - q2;
  int n = numA + numB;
  string ans;
  if (n == 1) {
    if (numA)
      cout << "a" << endl;
    else
      cout << "b" << endl;
    return 0;
  }
  for (int i = 0; i < n - 1; i++) {
    string sorg = ans + 'b';
    for (int j = i + 1; j < n; j++) {
      sorg += 'a';
    }
    cout << sorg << endl << flush;
    int num;
    cin >> num;
    if (num == 0) {
      return 0;
    }
    if (num == numB - 1) {
      if (i != n - 2) {
        ans += 'b';
        numB--;
      } else {
        if (num == 1) {
          ans += "bb";
        } else {
          ans += "ba";
        }
      }
    } else {
      if (i != n - 2) {
        ans += 'a';
        numA--;
      } else {
        if (num == 1) {
          ans += "aa";
        } else {
          ans += "ab";
        }
      }
    }
  }
  cout << ans << endl << flush;
}
