#include <bits/stdc++.h>
using namespace std;
long long power(long long a, long long n) {
  a %= 1000000007;
  if (n == 1) return a;
  if (n == 0) return 1;
  if (n % 2)
    return (a * (power((a * a) % 1000000007, n / 2) % 1000000007)) % 1000000007;
  return power((a * a) % 1000000007, n / 2) % 1000000007;
}
const long long inf = (long long)1e18;
long long inverse(long long x) { return power(x, 1000000007 - 2) % 1000000007; }
long long n;
vector<string> v;
void solve(long long pos, string ans) {
  if (pos > n) {
    v.push_back(ans);
    return;
  }
  for (long long i = 0; i < pos; ++i) solve(pos + 1, ans + (char)('a' + i));
}
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  cin >> n;
  solve(2, "a");
  sort(v.begin(), v.end());
  for (auto &x : v) cout << x << "\n";
  return 0;
}
