using System;
using System.Numerics;

// ulong is unsigned 64-bit: 2^64 - 1 is exactly its largest value.
ulong moves = ulong.MaxValue;
Console.WriteLine($"ulong:      {moves}");

// By default, arithmetic that overflows wraps round silently...
ulong wrapped = moves + 1;
Console.WriteLine($"wrapped:    {wrapped}");

// ...unless you ask for it to be checked.
try
{
    ulong next = checked(moves + 1);
    Console.WriteLine($"checked:    {next}");
}
catch (OverflowException)
{
    Console.WriteLine("checked:    OverflowException");
}

// UInt128, since .NET 7, is twice as wide: its maximum is the 128-disk count.
Console.WriteLine($"UInt128:    {UInt128.MaxValue}");

// BigInteger has no ceiling at all.
Console.WriteLine($"BigInteger: {BigInteger.Pow(2, 64) - 1}");