Theorem nnz

Description: A positive integer is an integer. (Contributed by NM, 9-May-2004)

	Ref	Expression
Assertion	nnz	$$⊢N\in \mathbb{N}\to N\in \mathbb{Z}$$

Proof

Step	Hyp	Ref	Expression
1		nnssz	$$⊢\mathbb{N}\subseteq \mathbb{Z}$$
2	1	sseli	$$⊢N\in \mathbb{N}\to N\in \mathbb{Z}$$