# How do I get the classical N1 object rather than N*? (NN)

Sage's global "NN" is the modern definition of the natural numbers (N0, which includes zero); how do I get instead an object representing the classical definition (N1 a.k.a. N*, which excludes zero)?

http://en.wikipedia.org/wiki/Natural_...

sage: NN

Non negative integer semiring

If I want to make further set subtractions, how do I do so? What trade-offs might I encounter typically with such operations?

sage: Set(NN) - Set([0]) Set-theoretic difference between Set of elements of Non negative integer semiring and {0}

If I were to make further set subtractions, what operations would become slow?