The famous 3X + 1

ThreexPlusOne.cs

internal class Program
{
	private const ulong limit = 1;
	private static void Main(string[] args)
	{
		if (args.Length < 1)
		{
			Console.WriteLine("No start number specified");
			return;
		}
		if (!ulong.TryParse(args[0], out ulong inputNumber))
		{
			Console.WriteLine("No valid start number: {0}", args[0]);
			return;
		}
		ulong iterations = 0;
		ulong maxvalue = inputNumber;
		ulong actual = inputNumber;
		while (actual > limit)
		{
			iterations++;
			if ((actual & limit) == limit)
			{
				actual *= 3;
				actual++;
			}
			else
			{
				actual >>= 1;
			}
			maxvalue = Math.Max(actual, maxvalue);
		}
		Console.WriteLine("{0} solved in {1} iterations", inputNumber, iterations);
		Console.WriteLine("Max value riched was {0}.", maxvalue);
	}
}

using System.Numerics;

internal class Program
{
	private static void Main(string[] args)
	{
		if (args.Length < 1)
		{
			Console.WriteLine("No start number specified");
			return;
		}
		if (!BigInteger.TryParse(args[0], out BigInteger inputNumber))
		{
			Console.WriteLine("No valid start number: {0}", args[0]);
			return;
		}
		BigInteger limit = 1;
		BigInteger iterations = 0;
		BigInteger maxvalue = inputNumber;
		BigInteger actual = inputNumber;
		while (actual > limit)
		{
			iterations++;
			if ((actual & limit) == limit)
			{
				actual *= 3;
				actual++;
			}
			else
			{
				actual >>= 1;
			}
			maxvalue = BigInteger.Max(actual, maxvalue);
		}
		Console.WriteLine("{0} solved in {1} iterations", inputNumber, iterations);
		Console.WriteLine("Max value riched was {0}.", maxvalue);
	}
}