#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int,int>;

int n;

void dfs(string s) {
  char end = s.back();
  
  if(s.length() >= n){
    cout << s << endl;
  } else {
    for(char c = 'a'; c <= end+1; ++c) {
      dfs(s + c);
    }
  }
  
}