28.12-02.Anaccil

using System;

class Anacci
{
    static void Main()
    {
        char firstLetter = char.Parse(Console.ReadLine());
        char secondLetter = char.Parse(Console.ReadLine());

        byte L = byte.Parse(Console.ReadLine());

        int firstIndex = (int)firstLetter - 64;
        int secondIndex = (int)secondLetter - 64;

        Console.WriteLine((char)(firstIndex + 64));

        if (L != 1)
        {
            for (int i = 1; i < L; i++)
            {
                for (int j = 0; j <= 1; j++)
                {
                    int newIndex = firstIndex + secondIndex;

                    if (newIndex > 26)
                    {
                        newIndex %= 26;
                    }

                    firstIndex = secondIndex;
                    secondIndex = newIndex;

                    if (j > 0) {
                        string whitespaces = new string(' ', i - 1);
                        Console.Write(whitespaces);
                    }

                    Console.Write((char)(firstIndex + 64));
                }

                Console.WriteLine();
            }
        }
    }
}