using System;
using System.Linq;

namespace P4.ConvertHexacimalToDecimal
{
    class Program
    {
        private static string hexNumbers = "0123456789ABCDEF";
        static void Main(string[] args)
        {
            Console.Write("Enter the hexadecimal number -> ");
            string hexNumber = Console.ReadLine().ToUpper();
            Console.WriteLine("The decimal number is -> " + ConvertHexadecimalToDecimal(hexNumber));
        }

        private static long ConvertHexadecimalToDecimal(string pHexNumber)
        {
            long numberInDec = 0;
            for (int i = 0; i < pHexNumber.Length; i++)
            {
                numberInDec += hexNumbers.IndexOf(pHexNumber[pHexNumber.Length - (i+1)]) * (long)Math.Pow(16, i);
            }
            return numberInDec;
        }
    }
}