import java.util.*;
import java.lang.Math;

class Sudoku{
    // numbers of the sudoku
    public ArrayList<Integer> numbers;

    // size of sudoku's side
    private int size;

    // constructor with ready sudoku
    Sudoku(StringBuilder strb){
        size = 4;

        numbers = new ArrayList<>();
        for(int i=0; i<size*size; i++){
            numbers.add(Character.getNumericValue(strb.charAt(i)));
        }
    }

    // constuctor with empty sudoku
    Sudoku(){
        size = 4;

        numbers = new ArrayList<>();
        // filling in the sudoku with a number -...a4a3a2a1 as index of
        // where it has no value(a1=1 if 1 is possible to be at that
        // spot and 0 if not. The same applies for a2, a3, a4 and so forth)
        StringBuilder strbNum = new StringBuilder();
        for(int i=size; i>0; i--){
            strbNum.append(Integer.toString(i));
        }

        for(int i=0; i<size*size; i++){
            numbers.add(-Integer.parseInt(strbNum.toString()));
        }
    }

    // return true if it's possible to add a number at that space
    public boolean check(int number, int place){
        if(number == -numbers.get(place)/(Math.pow(10, number-1)%10) && numbers.get(place)<0){
            return true;
        }
        return false;
    }

    // when a number has been added makes the changes to the rest of the sudoku
    public boolean optimize(){
        return false;
    }

    // checks the boxes for optimize
    private boolean checksTheBoxes(){
        int val;

        // check if any changes have been made
        boolean has_changed = false;
        // in each box it saves the four places
        ArrayList<Integer> places = new ArrayList<>();

        // first box
        places.add(0);
        places.add(1);
        places.add(4);
        places.add(5);
        for(Integer i : places){
            for(Integer j: places){
                if(i != j){
                    // val at i
                    int val_i = numbers.get(i);
                    int val_j = numbers.get(j);
                    if(val_i>0 && val_j<0){
                        if(-val_j/(Math.pow(10, val_i-1)%10) == val_i){
                            val_j += val_i*Math.pow(10, val_i-1);
                            has_changed = true;
                        }
                    }
                }
            }
        }

        // second box
        places.set(0, 2);
        places.set(1, 3);
        places.set(2, 6);
        places.set(3, 7);
        for(Integer i : places){
            for(Integer j: places){
                if(i != j){
                    // val at i
                    int val_i = numbers.get(i);
                    int val_j = numbers.get(j);
                    if(val_i>0 && val_j<0){
                        if(-val_j/(Math.pow(10, val_i-1)%10) == val_i){
                            val_j += val_i*Math.pow(10, val_i-1);
                            has_changed = true;
                        }
                    }
                }
            }
        }

        // third box
        places.set(0, 8);
        places.set(1, 9);
        places.set(2, 12);
        places.set(3, 13);
        for(Integer i : places){
            for(Integer j: places){
                if(i != j){
                    // val at i
                    int val_i = numbers.get(i);
                    int val_j = numbers.get(j);
                    if(val_i>0 && val_j<0){
                        if(-val_j/(Math.pow(10, val_i-1)%10) == val_i){
                            val_j += val_i*Math.pow(10, val_i-1);
                            has_changed = true;
                        }
                    }
                }
            }
        }

        // fourth box
        places.set(0, 10);
        places.set(1, 11);
        places.set(2, 14);
        places.set(3, 15);
        for(Integer i : places){
            for(Integer j: places){
                if(i != j){
                    // val at i
                    int val_i = numbers.get(i);
                    int val_j = numbers.get(j);
                    if(val_i>0 && val_j<0){
                        if(-val_j/(Math.pow(10, val_i-1)%10) == val_i){
                            val_j += val_i*Math.pow(10, val_i-1);
                            has_changed = true;
                        }
                    }
                }
            }
        }

        return has_changed;
    }

    // checks the rows for optimize
    private boolean rows(){
        int val;

        // check if any changes have been made
        boolean has_changed = false;
        // in each box it saves the four places
        ArrayList<Integer> places = new ArrayList<>();

        for(int k=0; k<4; k++){

            places.add(k);
            places.add(k+1);
            places.add(k+2);
            places.add(k+3);
            for(Integer i : places){
                for(Integer j: places){
                    if(i != j){
                        // val at i
                        int val_i = numbers.get(i);
                        int val_j = numbers.get(j);
                        if(val_i>0 && val_j<0){
                            if(-val_j/(Math.pow(10, val_i-1)%10) == val_i){
                                val_j += val_i*Math.pow(10, val_i-1);
                                has_changed = true;
                            }
                        }
                    }
                }
            }

        }
    }

}

class SudokuLogic{

    public Sudoku sudoku;
    SudokuLogic(StringBuilder strb){
         sudoku = new Sudoku(strb);
    }

    SudokuLogic(){
        sudoku = new Sudoku();
    }

    // printing the sudoku
    public void printSudoku(){
        for(int i=0; i<4; i++){
            for(int j=0; j<4; j++){
                if(sudoku.numbers.get(i*4 + j)>0){
                    System.out.print(Integer.toString(sudoku.numbers.get(i*4 + j)) + "  ");
                }
                else{
                    System.out.print("_  ");
                }
            }
            System.out.println();
        }
    }

    // to enter a number
    public void enterNumber(int number, int place){
        if(sudoku.check(number, place)){
            sudoku.numbers.set(place, number);

            // checks if sudoku has not been optimize(means it has no more optimization to take)
            boolean flag;
            do{
                flag = false;
                flag = sudoku.optimize();
            } while(flag == true);
        }
    }


}

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        StringBuilder strb = new StringBuilder("1234123412341234");
        SudokuLogic sudokuLogic = new SudokuLogic();

        sudokuLogic.printSudoku();
    }
}