using System;

​

    class Program

    {

        static void Main(string[] args)

        {

​

            int range = 13;

            Console.WriteLine("Start solving the puzzle.");

            for(var a = 0; a <= range; a++)

            {

                for(var b = 0; b <= range; b++)

                {

                    for(var c = 0; c <= range; c++)

                    {

                        for(var d = 0; d <= range; d++)

                        {

                            if(EqualEight(a,b))

                            {

                                //Console.WriteLine($"i {a} + j {b} = 8");

                                if(EqualThirteen(a, c))

                                {

                                    if(EqualEight(b, d))

                                    {

                                        if(EqualSix(c, d))

                                        {

                                        Console.WriteLine($"A: {a} b: {b} c: {c} d: {d}");

                                        }

                                    }

                                }

                            }

                        }

                    }   

                }

            }

        }

        static private bool EqualEight(int a, int b)

        {

            return a + b == 8;

        }

​

        static private bool EqualSix(int c, int d)

        {

            return c - d == 6;

        }

​

        static private bool EqualThirteen(int a, int c)

        {

            return a + c == 13;

        }

    }

​

​