HexadecimalToDecimalNumber

using System;
using System.Numerics;
namespace Hexadecimal_to_Decimal_Number
{
	class HexadecimalToDecimalNumber
	{
		public static void Main(string[] args)
		{
			string hex = Console.ReadLine();
			BigInteger dec = 0;
			int power = 1;
			for(int i = hex.Length - 1; i >= 0; i--)
			{

				int num;
				switch (hex[i])
				{
					case 'A': num = 10; break;
					case 'B': num = 11; break;
					case 'C': num = 12; break;
					case 'D': num = 13; break;
					case 'E': num = 14; break;
					case 'F': num = 15; break;
					default: num = (int)hex[i] - 48; break;
				}
				dec += num * power;
				power *= 16;
			}
			Console.WriteLine(dec);
			Console.Write("Press any key to continue . . . ");
			Console.ReadKey(true);
		}
	}
}