#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main(int argc, char * argv[])
{ const string letter[] = { "@", "a", "b", "c", "d", "e", "f", "g", "h", "i", "j",
                            "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u",
                            "v", "w", "x", "y", "z" };
  int N = atol(argv[1]);

  vector<string> * oldset = new vector<string>();
  if (N > 0)
    oldset->push_back(letter[1]);
  vector<string> * newset = new vector<string>();

  for (int i = 2; i <= N; i += 1)
  { 
    for (int j = 0; j < oldset->size(); j += 1)
    { string perm = oldset->at(j);
      for (int k = 0; k <= perm.length(); k += 1)
        newset->push_back(perm.substr(0, k) + letter[i] + perm.substr(k)); }

    swap(oldset, newset);
    newset->clear(); }

  for (int i = 0; i < oldset->size(); i += 1)
    cout << i << ": " << oldset->at(i) << "\n"; }