import java.util.*;

// Examples of recursive backtracking
public class Backtracking {
   public static void main(String[] args) {
      // fourAB();
      diceRoll(2);
   }
   
   // Prints all strings of length 4 composed of
   // only a's and b's
   public static void fourAB() {
      fourAB("");
   }
   
   // Prints all strings of length 4 composed of
   // only a's and b's starting with the given prefix
   private static void fourAB(String soFar) {
      if (soFar.length() == 4)  {  // base case
         System.out.println(soFar);
      } else {  // recursive case
         // choices: a, b
         fourAB(soFar + "a");
         fourAB(soFar + "b");
      }
   }


   // Prints all possible outcomes of rolling the given
   // number of six-sided dice in [#, #, #] format.
   // pre: dice >= 0
   public static void diceRoll(int dice) {
      diceRoll(new ArrayList<>(), dice);
   }
   
   // Prints all possible outcomes of rolling the given number
   // of six-sided dice in [#, #, #] format with chosen
   // as the prefix of all printed.
   private static void diceRoll(List<Integer> chosen, int dice) {
      if (dice == 0) {  // base case
         System.out.println(chosen);
      } else  {  // recursive case
         // choices: 1 - 6
         for (int i = 1; i <= 6; i++) {           // for each choice:
            chosen.add(i);                        //      choose
            diceRoll(chosen, dice - 1);           //      explore
            chosen.remove(chosen.size() - 1);     //      unchoose
            
            // chosen.remove(i) does NOT work - we want to remove the
            // last thing (the choice we just added). A stack would be
            // even better than a list here!
         }
      }
   }
  
}