/*************************************************************************
*  Compilation:  javac Permutation1.java
*  Execution:    java Permutation1 N k
*  
*  Enumerates all permutations of size k chosen from N elements.
*
*  % java Permutation1 4 2 | sort
*  ab
*  ac
*  ad
*  ba 
*  bc
*  bd
*  ca
*  cb
*  cd
*  da
*  db 
*  dc 
*
*  Limitations
*  -----------
*    *  Assumes N <= 52
*
*************************************************************************/

public class Permutation1 
{

   public static void choose(char[] a, int R) 
   { 
      enumerate(a, a.length, R); 
   }

   private static void enumerate(char[] a, int n, int r) 
   {
      if (r == 0) 
      {
          for (int i = n; i < a.length; i++)
              System.out.print(a[i]);
          System.out.println();
          return;
      }

      for (int i = 0; i < n; i++) 
      {
          swap(a, i, n-1);
          enumerate(a, n-1, r-1);
          swap(a, i, n-1);
       }
   }  

   // helper function that swaps a[i] and a[j]
   public static void swap(char[] a, int i, int j) 
   {
      char temp = a[i];
      a[i] = a[j];
      a[j] = temp;
   }


   // sample client
   public static void main(String[] args) 
   {
      int N = Integer.parseInt(args[0]);
      int k = Integer.parseInt(args[1]);
      String elements = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

      char[] a = new char[N];

      for (int i = 0; i < N; i++)
          a[i] = elements.charAt(i);
      choose(a, k);
   }
}