Durankulak Numbers

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

class Program
{
    static void Main()
    {
        string number = Console.ReadLine();

        List<int> digits = new List<int>();
        int bigLetter = 0;
        int smallLetter = 0;

        foreach (var ch in number)
        {
            if ( ch > 96 && ch < 123)
            {
                smallLetter = (ch - 96) * 26;
            }
            if ( ch >64 && ch < 91)
            {
                bigLetter = ch - 65 + smallLetter;
                digits.Add(bigLetter);
                smallLetter = 0;
                bigLetter = 0;
            }
        }
        digits.Reverse();
        BigInteger result = 0;
        for (int i = 0; i < digits.Count; i++)
        {
            result += (digits[i] * CalculatePower(i));
        }

        Console.WriteLine(result);
    }
    static BigInteger CalculatePower(int index)
    {
        BigInteger pow = 1;
        for (int i = 0; i < index; index--)
        {
            pow *= 168;
        }
        return pow;
    }
}