// ADD NEEDED IMPORT STATEMENTS HERE

public class LatinSquares {
    
    ///////////////////
    // INNER CLASSES //
    ///////////////////
    
    public static class Choice {
        private int numChosen;
        
        private Choice(int numChosen) {
            //// ADD CODE HERE ////
        }
        
        public static Choice firstChoice() {
            //// ADD CODE HERE ////
        }
        
        public Choice nextChoice() {
            //// ADD CODE HERE ////
        }
        
        public boolean unconsideredChoicesExist() {
            //// ADD CODE HERE ////
        }
        
        protected Choice clone() {
            //// ADD CODE HERE ////
        }
        
        public String toString() {
            //// ADD CODE HERE ////
        }
    }
    
    public static class StackOfChoices implements Iterable<Choice> {    
        
        private Choice[][] choices;
        //// ADD ADDITIONAL INSTANCE VARIABLES HERE ////
        
        public StackOfChoices(int n) {
            //// ADD CODE HERE ////
        }
        
        public boolean isEmpty() {
            //// ADD CODE HERE ////
        }
        
        public int size() {
            //// ADD CODE HERE ////
        }
        
        public void push(Choice choice) {
            //// ADD CODE HERE ////
        }
        
        public Choice peek() {
            //// ADD CODE HERE ////
        }
        
        public Choice pop() {
            //// ADD CODE HERE ////
        }
        
        public Iterator<Choice> iterator() {
            //// ADD CODE HERE ////
        }
        
        public boolean mightHaveSolutionWith(Choice choice) {
            //// ADD CODE HERE ////
        }
        
        
        public String toString() {
            //// ADD CODE HERE ////
        }
    }
    
    ////////////////////////
    // INSTANCE VARIABLES //
    ////////////////////////
    
    private static int n = 0;  
    private StackOfChoices stackOfChoicesMade;
    private Stack<String> stackOfSolutions;
    
    public LatinSquares(int size) {
        LatinSquares.n = size;
        stackOfChoicesMade = new StackOfChoices(n);
        stackOfSolutions = new Stack<String>();
    }
    
    public boolean solutionFound() {
        //// ADD CODE HERE //// 
    }
    
    public void solve() throws InterruptedException {
        
        Choice choice = Choice.firstChoice();   

        while (true) {

            if (stackOfChoicesMade.mightHaveSolutionWith(choice)) {
                stackOfChoicesMade.push(choice);
                choice = Choice.firstChoice();                
            } 
            else if (choice.unconsideredChoicesExist()) {
                choice = choice.nextChoice();
            }
            else {                                    
                if (stackOfChoicesMade.isEmpty())   // Here, you intend to pop to backtrack if you can.
                    break;                          // If you can't (because the stack is empty), you are done! 
                    
                choice = stackOfChoicesMade.pop().nextChoice();    // If the pop is safe, pick up where you 
                                                                   // left off with your last choice.
                                                                   // (i.e., choose the next choice after that one)
            }   
            
            if (solutionFound()) {    
                reactToSolutionFound();
                choice = stackOfChoicesMade.pop();    // normally we check to make sure -- but it's safe to pop.. why? 
                choice = choice.nextChoice();         // keep going to try to find other solutions 
            }            
        }
    }
    
    public void reactToSolutionFound() {
        //// ADD CODE HERE ////
    }
    
    public static void main(String[] args) throws InterruptedException {
        System.out.println("Enter n: ");
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        scanner.close();
        
        LatinSquares latinSquares = new LatinSquares(n);
        latinSquares.solve();
        
        System.out.println("\nSolutions:\n");
        for (String solution : latinSquares.stackOfSolutions) {
            System.out.println(solution);
        }
        System.out.println(latinSquares.stackOfSolutions.size() + " solutions found!\n");
        
    }

}