Performing Operations And Assigning Values To A BigInteger Type?

.Net 4.0
Option Strict On
Option Explicit On

This works perfectly:

Dim N As BigInteger
N = 28 'Put whatever value you want in for N.
Write((BigInteger.Log(N) / BigInteger.Log(2) + 1) / 2)

This does not work:

Dim Result As BigInteger = (BigInteger.Log(N) / BigInteger.Log(2) + 1) / 2

This gives an error during the build (despite the variable being declared as a BigInteger and the operation working perfectly well when I am not assigning it to a variable, it tells me I can't convert a Double to a BigInteger) and I have to do this:

Dim Result As BigInteger = CType((((BigInteger.Log(N) / BigInteger.Log(2)) + 1) / 2), BigInteger)

This if course gives a different, that is, incorrect result.'This doesn't work either.

Dim Result As BigInteger = BigInteger.Log(N)
'I can do this:
Dim ResultString As String = BigInteger.Log(N).ToString
'But then parsing the string fails

[code]....