Loops_15_HexadecimalToDecimal

static void Main()
        {
            string hexNumber = Console.ReadLine();
            long decNumber = 0;
            long power = 1;
            for (int i = hexNumber.Length - 1; i >= 0; i--)
            {
                int num;
                switch (hexNumber[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)hexNumber[i] - 48; break;
                }
                decNumber += num * power;
                power *= 16;
            }
            Console.WriteLine(decNumber);
        }