Danuci

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _01.Danuci
{
    class Program
    {
        static void Main(string[] args)
        {
            int pinCod = int.Parse(Console.ReadLine());
            int numberOfHash = int.Parse(Console.ReadLine());

            int secretCod = (500 + (pinCod % 1000)) / 10;

            int counterOfHash = 0;
            int cod = 0;

            for (char a = 'a'; a <= 'z'; a++)
            {
                for (char b = 'a'; b <= 'z'; b++)
                {
                    for (int c = 0; c <= 9; c++)
                    {
                        for (char d = 'a'; d <= 'z'; d++)
                        {
                            cod = (a + b + c) - d;
                            if (a != b && (cod == secretCod))
                            {
                                Console.Write("{0}{1}{2}{3}", a, b, c, d);
                                counterOfHash++;

                                if(counterOfHash == numberOfHash)
                                {
                                    return;
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}