Substitute

using System;

namespace Subtitude
{
    class Program
    {
        static void Main(string[] args)
        {
            int a = int.Parse(Console.ReadLine());
            int b = int.Parse(Console.ReadLine());
            int c = int.Parse(Console.ReadLine());
            int d = int.Parse(Console.ReadLine());
            int counter = 0;

            for (int k = a; k < 9; k++)
            {
                for (int l = 9; l >= b; l--)
                {
                    for (int m = c; m < 9; m++)
                    {
                        for (int n = 9; n >= d; n--)
                        {
                            if (k % 2 == 0 && m % 2 == 0 && l % 2 == 1 && n % 2 == 1)
                            {
                                if (k == m && l == n)
                                {
                                    Console.WriteLine("Cannot change the same player.");
                                }
                                else
                                {
                                    Console.WriteLine($"{ k}{ l} - { m}{ n}");

                                    if (++counter == 6)
                                    {
                                        Environment.Exit(0);
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}