Numerology (100/100)

using System;
using System.Collections.Generic;
using System.Linq;

namespace Numerology
{
    class Numerology
    {
        static void Main()
        {
            string input = Console.ReadLine();
            string[] splitInput = input.Split(' ', '.');
            UInt64 dateProduct = Convert.ToUInt64(splitInput[0].ToString()) *
                Convert.ToUInt64(splitInput[1].ToString())
               * Convert.ToUInt64(splitInput[2].ToString());
            if (Convert.ToUInt64(splitInput[1].ToString()) % 2 != 0)
            {
                dateProduct *= dateProduct;
            }
            UInt64 usernameWeight = 0;
            Dictionary<char,int> dict = new Dictionary<char, int>();
            char smallLetter = 'a';
            char bigLetter = 'A';
            for (int i = 1; i <= 26; i++,smallLetter++,bigLetter++)
            {
                dict.Add(smallLetter,i);
                dict.Add(bigLetter,i*2);
            }
            for (int i = 0; i < splitInput[3].Length; i++)
            {
                if (dict.ContainsKey(splitInput[3][i]))
                {
                    usernameWeight += Convert.ToUInt64(dict[splitInput[3][i]]);
                }
                else
                {
                    usernameWeight += Convert.ToUInt64(splitInput[3][i].ToString());
                }
            }
            UInt64 initialSum = usernameWeight + dateProduct;
            while (initialSum > 13)
            {
                int[] nums = Array.ConvertAll(initialSum.ToString().ToArray(), x => (int)x - 48);
                initialSum = Convert.ToUInt64(nums.Sum());
            }
            Console.WriteLine(initialSum);
        }
    }
}