using System;

public class Program

{

    public static void Main()

    {

        PrintAllKLengthStringForNSetChars(new char[]{'a','b'},2);

    }

    public static void PrintAllKLengthStringForNSetChars(char[] chArr, int k){

        Console.WriteLine("Sets for [{0}] of Length {1} are:",chArr.ToString(),k);

        PrintAllKLengthStringForNSetChars(chArr,chArr.Length,k,"");

    }

    public static void PrintAllKLengthStringForNSetChars(char[] chArr,int n, int k, string prefix){

        if(k==0){

            Console.WriteLine(prefix);

            return;

        }

        for(int i=0;i<n;i++){

            String newPrefix = prefix + chArr[i];

            PrintAllKLengthStringForNSetChars(chArr,n,k-1,newPrefix);

        }

    }

}